Single crystals of the Kitaev spin-liquid candidate $α$-RuCl$_3$ have been studied to determine low-temperature bulk properties, structure and the magnetic ground state. Refinements of x-ray diffraction data show that the low temperature crystal structure is described by space group $C2/m$ with a nearly-perfect honeycomb lattice exhibiting less than 0.2 \% in-plane distortion. The as-grown single crystals exhibit only one sharp magnetic transition at $T_{N}$ = 7~K. The magnetic order below this temperature exhibits a propagation vector of $k$ = (0, 1, 1/3), which coincides with a 3-layer stacking of the $C2/m$ unit cells. Magnetic transitions at higher temperatures up to 14~K can be introduced by deformations of the crystal that result in regions in the crystal with a 2-layer stacking sequence. The best fit symmetry allowed magnetic structure of the as-grown crystals shows that the spins lie in the $ac$-plane, with a zigzag configuration in each honeycomb layer. The three layer repeat out-of-plane structure can be refined as a 120$^o$ spiral order or a collinear structure with spin direction 35$^o$ away from the $a$-axis. The collinear spin configuration yields a slightly better fit and also is physically preferred. The average ordered moment in either structure is less than 0.45(5) $μ_B$ per Ru$^{3+}$ ion.
Magnetically pure spinel compound ${\rm LiV_2O_4}$ is a rare $d$-electron heavy fermion. Measurements on single crystals are needed to clarify the mechanism for the heavy fermion behavior in the pure material. In addition, it is known that small concentrations ($< 1$ mol%) of magnetic defects in the structure strongly affect the properties, and measurements on single crystals containing magnetic defects would help to understand the latter behaviors. Herein, we report flux growth of ${\rm LiV_2O_4}$ and preliminary measurements to help resolve these questions. The magnetic susceptibility of som…
Using magnetic torque measurement on a NaNiO2 single crystal, we have established the magnetic phase diagram of this triangular compound. It presents 5 different phases depending on the temperature (4 K - 300 K) and magnetic field (0 - 22 T) revealing several spin reorientations coupled to different magnetic anisotropies.
The thermodynamic Bethe ansatz equations of the Coqblin-Schrieffer model have been solved numerically. The full N=6 (J=5/2) degeneracy of the Hund's rule ionic ground state of Ce is taken into account. Results for the temperature dependent magnetic susceptibility parallel and perpendicular to the crystal axis are presented. The deviations, due to the Kondo effect, to the non-interacting ion results are pointed out.
We report the anisotropic magnetic properties of the ternary compound ErAl$_2$Ge$_2$. Single crystals of this compound were grown by high temperature solution growth technique,using Al:Ge eutectic composition as flux. From the powder x-ray diffraction we confirmed that ErAl$_2$Ge$_2$ crystallizes in the trigonal CaAl$_2$Si$_2$-type crystal structure. The anisotropic magnetic properties of a single crystal were investigated by measuring the magnetic susceptibility, magnetization, heat capacity and electrical resistivity. A bulk magnetic ordering occurs around 4 K inferred from the magnetic susc…
In this paper, we study the effect of both an external and crystal magnetic fields for a superlattice with mixed spins (1/2, 1), using Monte Carlo simulations. The ground state phase diagrams, in the external magnetic field, coupling constant and the crystal magnetic field planes, were established. The effect of increasing temperatures has also been established showing the behavior of the magnetizations and susceptibilities, for fixed crystal field values. In particular, the obtained results as well as in the ground state phase diagrams, as for non null temperature are obtained for fixed exter…
Quantum fluctuations become particularly relevant in highly frustrated quantum magnets and can lead to new states of matter. We provide a simple and robust scenario for inducing magnetic vortex crystals in frustrated Mott insulators. By considering a quantum paramagnet that has a gapped spectrum with six-fold degenerate low energy modes, we study the magnetic field induced condensation of these modes. We use a dilute gas approximation to demonstrate that a plethora of multi-$\mathbf{Q}$ condensates are stabilized for different combinations of exchange interactions. This rich quantum phase diag…
The anisotropic magnetic properties of the antiferromagnetic compound CePd$_2$Ge$_2$, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of magnetization and resistivity is observed along the two principal crystallographic directions viz., [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin re-orientation at 13.5 T for …
We report on the crystal growth of the quasi one-dimensional quantum spin chain compound SrCuO$_{2}$ and its doped variants containing magnetic cobalt (0.25%, 0.5%, 1% and 2.5%) and non-magnetic zinc (0.5\% and 1\%) impurities. Crystals are grown using the travelling solvent floating zone (TSFZ) method in a four-mirror optical furnace. Some crucial factors, key to the stability of a TSFZ process, including the choice of solvent composition and its associated melting behavior, are discussed in detail. The grown crystals were characterized using x-ray powder diffraction, scanning electron micros…
Single crystal of CeMg$_{12}$ is obtained by Bridgman method. CeMg$_{12}$ crystallizes in the tetragonal structure with space group $I4/mmm$ (#139). The Laue pattern confirms the tetragonal crystal structure of CeMg$_{12}$. We have studied the magnetic properties by measuring magnetic susceptibility, magnetization, heat capacity and electrical transport. Specific heat measurement shows that the compound orders at 1.2 K. We have measured the magnetic susceptibility in the temperature range 1.8 to 300 K, and the susceptibility data show that [100] crystallographic direction is the easy axis of m…
We combine two aspects of magnetic frustration, multiferroicity and emergent quasi-particles in spin liquids, by studying magneto-electric monopoles. Spin ice offers to couple these emergent topological defects to external fields, and to each other, in unusual ways, making possible to lift the degeneracy underpinning the spin liquid and to potentially stabilize novel forms of charge crystals, opening the path to a "magnetic crystallography". In developing the general phase diagram including nearest-neighbour coupling, Zeeman energy, electric and magnetic dipolar interactions, we uncover the em…
Temperature dependencies of magnetic susceptibility in a trigonal single crystal of erbium aluminum borate were measured in the temperature range of 2 - 15 K at the external field of 100 Oe applied along the second- and third-order crystallographic axes. Analysis of the experimental data allows to identify the Van Vleck contribution to the susceptibility. The influence of spin correlations on the magnetic susceptibility has been identified. It has been estimate the negative paramagnetic Curie-Weiss temperature.
We have grown the single crystals of LaAu$_{2}$In$_{4}$ and CeAu$_{2}$In$_{4}$ by high temperature solution method and report on the anisotropic magnetic behavior of CeAu$_{2}$In$_{4}$ . The compounds crystallize in an orthorhombic structure with space group \textit {Pnma}. LaAu$_{2}$In$_{4}$ shows a Pauli-paramagnetic behavior. CeAu$_{2}$In$_{4}$ do not order down to 1.8 K. The easy axis of magnetization for CeAu$_{2}$In$_{4}$ is along [010] direction. The magnetization data is analyzed on the basis of crystalline electric field (CEF) model.
Lattice Wigner crystal states stabilized by long-range Coulomb interactions have recently been realized in two-dimensional moiré materials. We employ large-scale unrestricted Hartree-Fock techniques to unveil the magnetic phase diagrams of honeycomb lattice Wigner crystals. For the three lattice filling factors with the largest charge gaps, n = 2/3, 1/2, 1/3, the magnetic phase diagrams contain multiple phases, including ones with non-collinear and non-coplanar spin arrangements. We discuss magnetization evolution with external magnetic field, which has potential as an experimental signature o…
It is demonstrated that there is anti-ferromagnetic spin-spin interaction between nearest electrons in the 2D Wigner crystal. This is also valid for the Wigner liquid - the state with destroyed long-range order but preserved short-range one. We calculate the value of the anti-ferromagnetic interaction (both analytically and numerically) and discuss a possible magnetic state of the Wigner crystal. This state can be strongly influenced by the spin-Peierls mechanism.
Magnetic defects have pronounced effects on the magnetic properties of the face-centered cubic compound LiV2O4. The magnetic defects arise from crystal defects present within the normal spinel structure. High-energy x-ray diffraction studies were performed on LiV2O4 single crystals to search for superstructure peaks or any other evidence of periodicity in the arrangement of the crystal defects present in the lattice. Entire reciprocal lattice planes are mapped out with help of synchrotron radiation. No noticeable differences in the x-ray diffraction data between a crystal with high magnetic de…
Single crystals of CeGe and its non-magnetic analogue LaGe have been grown by Czochralski method. CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group \textit{Pnma} (#62). The anisotropic magnetic properties have been investigated on well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy reflecting the orthorhombic crystal structure. The magnetization measuremen…
The magnetic behavior of single-crystalline CeCuGa3 has been investigated. The compound forms in a tetragonal BaAl4-type structure consisting of rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type structure, in which the Ce ion are surrounded by different Cu and Ga layers and the inversion symmetry is lost. In the literature conflicting reports about the magnetic order of CeCuGa3 have been published. Single crystals with the centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 …
Flexible magnetic materials with robust and controllable perpendicular magnetic anisotropy (PMA) are highly desirable for developing flexible high-performance spintronic devices. However, it is still challenge to fabricate PMA films through current techniques of direct deposition on polymers. Here, we report a facile method for synthesizing single-crystal freestanding SrRuO3 (SRO) membranes with controlled crystal structure and orientation using water-soluble Ca3-xSrxAl2O6 sacrificial layers. Through cooperative effect of crystal structure and orientation engineering, flexible SrRuO3 membranes…
Mn1-xZnxCr2O4 (0<x<1) single crystals have been grown by the chemical vapor transport (CVT) method. The crystallographic, magnetic, and thermal transport properties of the single crystals were investigated by the room-temperature X-ray diffraction, magnetization M(T) and specific heat CP(T) measurements. Mn1-xZnxCr2O4 crystals show a cubic structure, the lattice constant a decreases with the increasing content x of the doped Zn2+ ions and follows the Vegard law. Based on the magnetization and heat capacity measurements, the magnetic evolution of Mn1-xZnxCr2O4 crystals has been discussed. For 0…
We report the single crystal growth and anisotropic magnetic properties of the tetragonal RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) compounds which crystallize in the ThCr$_2$Si$_2$ type crystal structure with the space group \textit{I4/mmm}. The single crystals of RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) were grown by self-flux method using Ag:Ge binary alloy as flux. From the magnetic studies on single crystalline samples we have found that PrAg$_2$Ge$_2$ and NdAg$_2$Ge$_2$ order antiferromagnetically at 12 K and 2 K respectively, thus corroborating the earlier polycrystalline results. SmAg$_2$Ge$_2$ also …
We report single-crystal neutron diffraction study of the magnetic structure of the multiferroic compound YbMnO$_3$, a member of the hexagonal manganite family, in zero-field and under a magnetic field applied along the $c$-axis. We propose a scenario for the zero-field magnetic ordering and for the field-induced magnetic reorientation of the Mn and of the two Yb on distinct crystallographic sites, compatible with the macroscopic measurements, as well as with previous powder neutron diffraction experiment and results from other techniques (optical second harmonic generation, Mössbauer spectros…
Detailed anisotropic resistivity and heat capacity measurements down to ~0.4 K and up to 140 kOe are reported for a single crystalline YbAgGe. Based on these data YbAgGe, a member of the hexagonal RAgGe series, can be classified as new, stoichiometric heavy fermion compound with two magnetic ordering temperatures below 1 K and field-induced non-Fermi-liquid behavior above 45-70 kOe and 80-110 kOe for $H || (ab) and H || c respectively.
Single crystals of Fe$_{1/4}$TaS$_{2}$ have been studied by using magneto-optical (MO) imaging and radio-frequency (rf) magnetic susceptibility, $χ$. Real time MO images reveal unusual, slow dynamics of dendritic domain formation, the details of which are strongly dependent upon magnetic and thermal history. Measurements of $χ(T)$ show well-defined, local moment ferromagnetic transition at $T\approx 155$ K as well as thermal hysteresis for 50 K$<T<$60 K. This temperature range corresponds to the domain formation temperature as determined by MO. Together these observations provide strong eviden…
Measurements of DC magnetization, AC susceptibility and Hall effect of $Pr_{0.7}Sr_{0.3}MnO_3$ single crystal are reported. The various features are discussed in terms of competing electronic and spin ordering phase transitions, in particular concerning the $e_g$ and $t_{2g}$ competition and its effect on spin ordering.
The ferrimagnetic spinel Mn3O4 exhibits large and anisotropic changes in electronic and structural properties in response to an applied magnetic field. These changes are thought to result from the field-dependent tuning---via strong spin-lattice coupling---between two nearly degenerate magnetostructural phases. Recent variable-magnetic-field studies of Mn3O4 have been performed on melt-grown crystals, which can exhibit twin domains due to a Jahn-Teller structural transition below the melting temperature. Because of the near degeneracy of the magnetostructural phases, however, strain associated…
In order to investigate the anisotropic magnetic properties of CeAg$_2$Ge$_2$, we have successfully grown the single crystals, for the first time, by high temperature solution growth (flux) method. We have performed a detailed study of the grown single crystals by measuring their electrical resistivity, magnetic susceptibility, magnetization, specific heat and magnetoresistance. A clear anisotropy and an antiferromagnetic transition at $T_{\rm N}$ = 4.6 K have been observed in the magnetic properties. The magnetic entropy reaches $R$ ln 4 at 20 K indicating that the ground state and the first …
We present an extensive powder and single-crystal neutron scattering investigation of the crystallographic structure and magnetic order of the frustrated metallic $f$-electron magnet UNi$_4$B. We carry out a full refinement of the crystallographic structure and conclude that the low-temperature lattice symmetry is orthorhombic (space group Pmm2; cell parameters: $a = 6.963(4)~Å$ , $b = 14.793(9)~Å$ , $c = 17.126(8)~Å$). We determine the magnetically ordered structure, concluding that below $T_\mathrm{N} = 19.5~\mathrm{K}$ the material undergoes a transition into a partially ordered antiferroma…
Symmetry analysis of the Dzyaloshinskii-Moriya (DM) interaction in MnSi-type cubic crystals demonstrates that the magnetic moments are tilted periodically, producing a weak antiferromagnetic pattern, when the helix is unwound by magnetic field. The tilt angles of four Mn sublattices are determined by a component of the DM vector perpendicular to that one responsible for helical spiraling; both components have been evaluated using a simple model. It is shown that the tilting should induce pure magnetic reflections 00l, l=2n+1 in neutron or x-ray magnetic scattering, and the structure factors of…
The magnetic structure of the spin-chain antiferromagnet SrCo2V2O8 is determined by single-crystal neutron diffraction experiment. The system undergoes magnetic long range order below T_N = 4.96 K. The moment of 2.16μ_B per Co at 1.6 K in the screw chain running along the c axis alternates in the c-axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetically along the other in-plane axis. This magnetic configuration breaks the 4-fold symmetry of the tetragonal crystal structure and leads to two equally populated magnetic twins w…
The magnetic structure of CsCo2Se2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector (0,0,1) was observed at T_N = 78 K. The Co magnetic moment 0.772(6) μ_B at 10 K pointing in the basal plane couples ferromagnetically in the plane which stacks antiferromagnetically along the c direction. Tuning and suppressing the interplane antiferromagnetic interaction may be crucial to induce the material to a superconducting state.
We explore the magnetic properties of isolated a-b planes of trinuclear organometallic crystals, Mo3S7(dmit)3, in which an interplay of strong electronic correlations and spin molecular-orbital coupling (SMOC) occurs. The magnetic properties can be described by a XXZ+120, S=1 Heisenberg model on a honeycomb lattice with single-spin anisotropy, D, which depends strongly on SMOC. Based on ab initio estimates of SMOC in Mo3S7(dmit)3 crystals, we predict that the honeycomb layers of Mo3S7(dmit)3 are Neel ordered. However, in materials with a greater degree of magnetic frustration, Neel order can g…
Using Path Integral Monte Carlo, we have calculated exchange frequencies as electrons undergo ring exchanges of 2, 3 and 4 electrons in a ``clean'' 3d Wigner crystal (bcc lattice) as a function of density. We find pair exchange dominates and estimate the critical temperature for the transition to antiferromagnetic ordering to be roughly $1 \times 10^{-8}$Ry at melting. In contrast to the situation in 2d, the 3d Wigner crystal is different from the solid bcc 3He in that the pair exchange dominates because of the softer interparticle potential. We discuss implications for the magnetic phase diag…
High temperature crystal structure of UPt$_2$Si$_2$ determined using single-crystal neutron diffraction at 400 K is reported. It is found that the crystal structure remains of the primitive tetragonal CaBe$_2$Ge$_2$ type with the space group P4/$n m m. Anisotropic displacement factors of the Pt atoms at the 2a (3/4 1/4 0) and Si atoms at the 2c (1/4 1/4 z) Wyckoff sites are found to be anomalously large.
Studies of diffuse magnetic scattering largely benefit from the use of a multi-detector covering wide scattering angles. Therefore, the different contributions to the diffuse scattering that originate from magnetic, nuclear coherent, and nuclear spin-incoherent scattering can be separated by the so-called XYZ-polarization analysis. In the past this method has been successfully applied to the analysis of diffuse scattering by polycrystalline samples of magnetic disordered materials. Single crystal studies that exploit the vector properties of spin correlations are of particular interest for fur…
Graphene based nanostructures exhibit flat electronic energy bands in their single-particle spectrum. We consider interacting electrons in flat bands of zig-zag nanoribbons. We present a protocol for flat-band projection that yields interaction-only tight-binding models. We argue that, at low densities, flat bands can delocalize single-particle basis states to support ferromagnetic quantum crystal ground states.
We investigate two holes in the the $t_{2g}$ levels of a square-lattice Mott insulator with strong spin-orbit coupling. Exact diagonalization of a spin-orbital model valid at strong onsite interactions, but arbitrary spin-orbit coupling and crystal field is complemented by an effective triplon model (valid for strong spin-orbit coupling) and by a semiclassical variant of the model. We provide the magnetic phase diagram depending on crystal field and spin-orbit coupling, which largely agrees for the semiclassical and quantum models, as well as excitation spectra characterizing the various phase…
We have investigated the magnetic and dielectric properties of Ca$_2$CoSi$_2$O$_7$ crystal. The dielectricity and magnetism of Ca$_2$CoSi$_2$O$_7$ are strongly coupled below a canted antiferromagnetic transition temperature ($T_{\rm N}$): Magnetic fields induce electric polarization below $T_{\rm N}$. Interestingly, the magnetic-field-induced electric polarization is detected even without poling electric fields. Below $T_{\rm N}$, a canted antiferromagnetic-paramagnetic transition is induced by magnetic fields. The large magnetocapacitance is observed around $T_{\rm N}$. The origin of the larg…
We report a study on the temperature dependence of the charge-neutral crystal field (dd) excitations in cupric oxide, using nonresonant inelastic x-ray scattering (IXS) spectroscopy. Thanks to a very high energy resolution (60 meV), we observe thermal effects on the dd excitation spectrum fine structure between temperatures of 10-320 K. With an increasing temperature, the spectra broaden considerably. We assign the temperature dependence of the dd excitations to the relatively large electron-phonon coupling.
The thermodynamic Bethe ansatz equations for the Coqblin-Schrieffer model have been solved for the first time to obtain the magnetic susceptibility in the presence of crystal fields for non-zero temperatures. For the case of N = 4 effective ionic states an analytic expression for the limiting values of the pseudo-energies has been found facilitating the numerical solution for various crystal and magnetic field configurations. The single-impurity model applies to a wide range of dense Kondo systems and has been used before to explain apparent non-Fermi-liquid behavior. The flattening off of the…
The magnetic investigations as a function of temperature and magnetic field for the rubidium neodymium double tungstate RbNd(WO4)2 single crystal have been performed. The magnetization was measured in the temperature range from 4.2 to 100 K and for the magnetic field up to 1.5 T. The crystal field and exchange parameters were found.
The lineshape of crystal-field transitions in single crystals of Mn12ac molecular magnets is determined by the magnetic history. The absorption lines are symmetric and Gaussian for the non-magnetized state obtained by zero-field cooling (zfc). In the magnetized state which is reached when the sample is cooled in a magnetic field (fc), however, they are asymmetric even in the absence of an external magnetic field. These observations are quantitatively explained by inhomogeneous symmetrical (Gaussian) broadening of the crystal-field transitions combined with a contribution of off-diagonal compon…
We have grown the single crystal of PrRhAl$_4$Si$_2$, which crystallizes in the tetragonal crystal structure. From the low temperature physical property measurements like, magnetic susceptibility, magnetization, heat capacity and electrical resistivity, we found that this compound does not show any magnetic ordering down to 70~mK. Our crystal field calculations on the magnetic susceptibility and specific heat measurements reveal that the 9-fold degenerate $(2J+1)$ levels of Pr atom in PrRhAl$_4$Si$_2$, splits into 7 levels, with a singlet ground state and a well separated excited doublet state…
We show that the bulk transport magnetic current is generated by the moving magnetic kink crystal (chiral soliton lattice) formed in the chiral helimagnet under the static magnetic field applied perpendicular to the helical axis. The current is caused by the non-equilibrium transport momentum with the kink mass being determined by the spin fluctuations around the kink crystal state. An emergence of the transport magnetic currents is then a consequence of the dynamical off-diagonal long range order along the helical axis. We derive an explicit formula for the inertial mass of the kink crystal a…
Two-dimensional magnetic materials (2DMM) are significant for studies on the nature of 2D long range magnetic order but also for future spintronic devices. Of particular interest are 2DMM where spins can be manipulated by electrical conduction. Whereas Cr$_2$Si$_2$Te$_6$ exhibits magnetic order in few-layer crystals, its large band gap inhibits electronic conduction. Here we show that the defect-induced short-range crystal order in Cr$_2$Si$_2$Te$_6$ on the length scale below 0.6 nm induces substantially reduced band gap and robust semiconducting behavior down to 2 K that turns to metallic abo…
The magnetic properties of CoSi single crystals have been measured in a range of temperatures $T = 5.5 - 450$ K and magnetic field strengths $H \leq 11$ kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility $χ(T) = M(T)/H$ to be determined for a hypothetical "ideal" (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The $χ(T)$ value significantly increases in absolute value with decreasing temperature…
The magnetic strings in antiferromagnetic crystals with the spin $S = 1 /2$ differ from the magnetic polarons (ferrons) by the absence of the additional magnetic moment. We show that in the $S > 1 /2$ double exchange crystals with the antiferromagnetic $s-d$ exchange, a new type of magnetic strings appears, which possesses a magnetic moment. It is concentrated at the center of the string, and the magnetized string is, in its essence, the state intermediate between the string and the ferron. In antiferromagnetic manganites, this moment is by an order of magnitude larger than that of a magnetic …
SrRuO3 is a highly interesting material due to its anomalous-metal properties related with ferromagnetism and its relevance as conductive perovskite layer or substrate in heterostructure devices. We have used optical floating zone technique in an infrared image furnace to grow large single crystals of SrRuO3 with volumes attaining several hundred mm3. Crystals obtained for optimized growth parameters exhibit a high ferromagnetic Curie temperature of 165 K and a low-temperature magnetization of 1.6 muB at a magnetic field of 6 T. The high quality of the crystals is further documented by large r…
Using a novel technique of measuring direct rf power dissipation, the temperature and magnetic field dependence of rf absorption in superconducting single crystals of Bi_2Sr_2CaCu_2O_8 is studied. An unexpected, larger than normal state, dissipation is observed below Tc, which exhibits peaks at magnetic field dependent temperatures. An explanation is provided for this observation in terms of the energy required to decouple the intrinsic Josephson junctions in the crystals.
We grew the single crystal of stoichiometric Tm5Si2.0Ge2.0 using a Bridgeman method and performed XRD, EDS, magnetization, ac and dc magnetic susceptibilities, specific heat, electrical resistivity and XPS experiments. It crystallizes in orthorhombic Sm5Ge4-type structure. The mean valence of Tm ions in Tm5Si2.0Ge2.0 is almost trivalent. The 4f states is split by the crystalline electric field. The ground state exhibits the long range antiferromagnetic order with the ferromagnetically coupled magnetic moments in the ac plane below 8.01 K, while the exited states exhibit the reduction of magnet…
Millimeter size single crystals of double perovskite La2NiMnO6 (LNMO) were grown by the High Temperature Solution Growth Method. The magnetic measurements and polarized Raman spectra between 5 and 350K provide evidence that the crystals have high degree of Ni(2+)/Mn(4+)ordering, small amount of lattice defects and highest Tc = 288K reported so far for ferromagnetic double perovskites. At a microscopic level the crystals are heavily twinned and the effect of twinning on the Raman spectra is analyzed in detail.
The experimental results on the magnetic response of YBCO single crystals with unidirectional twin boundary planes in low magnetic fields (0.01 - 1 Oe) are discussed. The observed non-monotone temperature dependence of magnetization is interpreted within a plausible model of a system of the Josephson weak links in the twin boundary planes and on the basis of the order parameter anisotropy.
The crystal growth and the structural, transport and magnetic properties of the magnetically frustrated YbMn$_2$Sb$_2$ single crystals are reported. The crystals show a trigonal symmetry (space group $P\bar{3}m1$), where corrugated honeycomb layers of MnSb are separated by Yb atoms. No structural phase transition was observed down to 22~K. The resistivity measurements show a predominantly insulating behavior. The combined resistivity, dc susceptibility and heat capacity measurements confirm successive transitions at 230~K, 116~K and 27~K, being the transition at $T_N$=116~K due to the Mn$^{+2}…
We have successfully grown cm3-size single crystals of the metallic-ferromagnet Sm2Mo2O7 by the floating-zone method using an infrared-red image furnace. The growth difficulties and the remedies found using a 2-mirror image furnace are discussed. Magnetization studies along the three crystalline axes of the compound are presented and discussed based on our recent proposal of an ordered spin-ice ground state for this compound
We clarify the role of crystalline electric field (CEF) induced magnetic anisotropy in the ground state and spin-wave spectrum of cubic rare-earth materials with dominating isotropic magnetic exchange interactions. In particular we study the hexaboride NdB_6 which is shown to exhibit strong spin-quadrupolar coupling. The CEF scheme is analyzed and a non-collinear magnetization response is found. The spin orientation in the antiferromagnetically ordered ground-state is identified. Moreover, the spin excitations are evaluated and in agreement with inelastic neutron scattering a suppression of on…
Skyrmions are spatially localized magnetic swirls which carry a nonzero integer topological charge. We study crystals of skyrmions in a two-dimensional ferromagnet model with chiral interactions induced by the presence of broken inversion symmetry. We show that non-linear quartic mode-coupling terms allowed by symmetry enhances the Zeeman-field range over which the skyrmion-crystal phase remains stable. Furthermore, it leads to a significant dependence of the lattice constant of this spin crystal over this wide field range. Conduction electrons coupled to such a tunable spin crystal are shown …
We report structural and magnetic properties studies of large high quality single-crystals of the frustrated magnet, Nd$_2$Zr$_2$O$_7$. Powder x-ray diffraction analysis confirms that Nd$_2$Zr$_2$O$_7$ adopts the pyrochlore structure. Room-temperature x-ray diffraction and time-of-flight neutron scattering experiments show that the crystals are stoichiometric in composition with no measurable site disorder. The temperature dependence of the magnetic susceptibility shows no magnetic ordering at temperatures down to 0.5 K. Fits to the magnetic susceptibility data using a Curie-Weiss law reveal a…
Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group ${Cmcm}$ (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a N$\grave{\rm e}$el temperature $T_{\rm N}$ = 10K…
