Single crystals of R$_2$CoGa$_8$ series of compounds were grown, for the first time, by high temperature solution growth (flux) method. These compounds crystallize in a tetragonal crystal structure with the space group $P4/mmm$. It has been found that R$_2$CoGa$_8$ phase forms only with the heavier rare earths, starting from Gd with a relatively large $c/a$ ratio of $\approx$ 2.6. The resultant anisotropic magnetic properties of the compounds were investigated along the two principal crystallographic directions of the crystal viz., along [100] and [001]. The nonmagnetic compounds Y$_2$CoGa$_8$ and Lu$_2$CoGa$_8$ show diamagnetic behavior down to the lowest temperature (1.8 K) pointing out the non-magnetic nature of Co in these compounds and a relatively low density of electronic states at the Fermi level. Compounds with the magnetic rare earths order antiferromagnetically at temperatures lower than 30 K. The easy axis of magnetization for R$_2$CoGa$_8$ (R = Tb, Dy and Ho) is found to be along the [001] direction and it changes to [100] direction for Er$_2$CoGa$_8$ and Tm$_2$CoGa$_8$. The magnetization behavior is analyzed on the basis of crystalline electric field (CEF) model. The estimated crystal field parameters explains the magnetocrystalline anisotropy in this series of compounds.
In this study, we investigate the magnetic susceptibility, entropy, and isothermal magnetization curve of the spin-1/2 Heisenberg model on an anisotropic triangular lattice using the orthogonalized finite-temperature Lanczos method. In addition, we investigate the adiabatic magnetization curve and magnetocaloric effect. We estimate these physical quantities with sufficient accuracy in the thermodynamic limit, except at low temperatures. We observe a 1/3 magnetization plateau in the isothermal magnetization process, whereas the plateau is observed to have a slope in the adiabatic process. We sh…
The $S=1/2$ distorted diamond spin chain with the anisotropic ferromagnetic interaction is investigated using the numerical diagonalization and the level spectroscopy analysis. It is known that the system exhibits a plateau of the magnetization curve at the 1/3 of the saturation. The present study indicates that as the anisotropy is varied the quantum phase transition occurs between two different mechanisms of the 1/3 magnetization plateau. The phase diagram with respect to the anisotropy and the ferromagnetic coupling is also presented.
We investigate the adiabatic magnetization process of the one-dimensional $J-Q_{2}$ model with XXZ anisotropy $g$ in an external magnetic field $h$ by using density matrix renormalization group (DMRG) method. According to the characteristic of the magnetization curves, we draw a magnetization phase diagram consisting of four phases. For a fixed nonzero pair coupling $Q$, i) when $g<-1$, the ground state is always ferromagnetic in spite of $h$; ii) when $g>-1$ but still small, the whole magnetization curve is continuous and smooth; iii) if further increasing $g$, there is a macroscopic magnetiz…
We examine ground state properties of the spin-1/2 easy-axis Heisenberg model on the Shastry-Sutherland lattice with ferromagnetic transverse spin exchange using quantum Monte Carlo and degenerate perturbation theory. For vanishing transverse exchange, the model reduces to an antiferromagnetic Ising model that besides Neel order harbors regions of extensive ground state degeneracy. In the quantum regime, we find a dimerized phase of triplet states, separated from the Neel ordered phase by a superfluid. The quantum phase transitions between these phases are characterized. The magnetization proc…
We study a Kondo impurity model with additional uniaxial anisotropy D in a non-zero magnetic field B using the Numerical Renormalization Group (NRG). The ratio g_e/g_S of electron and impurity g-factor is regarded as a free parameter and, in particular, the special cases of a "local" (g_e=0) and "bulk" (g_e=g_S) field are considered. For a bulk field, the relationship between the impurity magnetization M and the impurity contribution to the magnetization M_imp is investigated. Furthermore, we study how the value of g_e affects the impurity magnetization curves. In case of an isotropic impurity…
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…
Magnetization and torque measurements were performed on CeCoIn$_5$ single crystals to study the mixed-state thermodynamics. These measurements allow the determination of both paramagnetic and vortex responses in the mixed-state magnetization. The paramagnetic magnetization is suppressed in the mixed state with the spin susceptibility increasing with increasing magnetic field. The dependence of spin susceptibility on magnetic field is due to the fact that heavy electrons contribute both to superconductivity and paramagnetism and a large Zeeman effect exists in this system. No anomaly in the vor…
We study the spin-3/2 Heisenberg model including easy-plane and exchange anisotropies in one and two dimensions. In the Ising limit, when the off-diagonal exchange interaction J is zero, the phase diagram in magnetic field is characterized by magnetization plateaus that are either translationally invariant or have a two-sublattice order, with phase boundaries that are macroscopically degenerate. Using a site factorized variational wave function and perturbational expansion around the Ising limit, we find that superfluid and supersolid phases emerge between the plateaus for small finite values …
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 study the effects of longitudinal magnetic field and temperature on the thermodynamic properties of two dimensional Heisenberg antiferromagnet on the honeycomb lattice in the presence of anisotropic Dzyaloshinskii-Moriya interaction and next nearest neighbor coupling exchange constant. In particular, the temperature dependence of specific heat have been investigated for various physical parameters in the model Hamiltonian. Using a hard core bosonic representation, the behavior of thermodynamic properties has been studied by means of excitation spectrum of mapped bosonic gas. The effect of D…
We present a detailed study of R3Ni2-xSn7 (R = La, Ce, Pr and Nd) single crystals by measurements of crystal structure, stoichiometry, temperature dependent magnetic susceptibility, magnetization, electrical resistivity, magnetoresistance, and specific heat. This series forms with partial Ni occupancy with x varying from ~ 0.1 for R = La to ~0.7 for R = Nd. The electrical resistivity of this series follows metallic behavior at high temperatures. Determination of clear anisotropies as well as antiferromagnetic ordering temperatures for R3Ni2-xSn7 (R = Ce, Pr and Nd) have been made. For Pr3Ni1.5…
We report temperature dependent magnetization and neutron diffraction measurements on the corundum related magnetoelectric antiferromagnet Mn$_{4}$Ta$_{2}$O$_{9}$. Measurements performed on a single crystalline specimen reveal that the magnetization is anisotropic, and a weak ferromagnetic component emerges well within the antiferromagnetically ordered state. Powder neutron diffraction measurements indicate that the magnetic structure comprises of antiferromagnetically coupled ferromagnetic chains of Mn$^{2+}$ spins aligned along the trigonal $c$ axis, in contrast to that reported in other iso…
We present a single-crystal neutron diffraction study on the Shastry-Sutherland lattice system TbB$_4$ at zero magnetic field and under pulsed high magnetic fields up to 35 T applied along the crystallographic $c$ axis. While our results confirm the magnetic structures at zero-field as well as those at the half- and full-magnetization plateaus, they offer new insight into the $\frac{2}{9}$- and $\frac{1}{3}$-magnetization plateaus observed in this system. A stripe model of polarized 4-spin-plaquettes whose stripe density proportionally increases with the macroscopic magnetization is in full ag…
Using infinite projected entangled-pair states (iPEPS), we show that the Shastry-Sutherland model in an external magnetic field has low-magnetization plateaus which, in contrast to previous predictions, correspond to crystals of bound states of triplets, and {\it not} to crystals of triplets. The first sizable plateaus appear at magnetization 1/8, 2/15 and 1/6, in agreement with experiments on the orthogonal-dimer antiferromagnet SrCu$_2$(BO$_3$)$_2$, and they can be naturally understood as regular patterns of bound states, including the intriguing 2/15 one. We also show that, even in a confin…
Using the density matrix renormalization group technique, we study spin superlattices composed of a repeated pattern of two spin-1/2 XXZ chains with different anisotropy parameters. The magnetization curve can exhibit two plateaus, a non trivial plateau with the magnetization value given by the relative sizes of the sub-chains and another trivial plateau with zero magnetization. We find good agreement of the value and the width of the plateaus with the analytical results obtained previously. In the gapless regions away from the plateaus, we compare the finite-size spin gap with the predictions…
Gapped 1/9 Magnetization Plateau in the Anisotropic Kagome Antiferromagnet Y-kapellasite
Université Paris-Saclay（巴黎萨克雷大学）；CNRS（法国国家科学研究中心）；Laboratoire de Physique des Solides（固体物理实验室）；Clarendon Laboratory, Department of Physics, University of Oxford（牛津大学克拉伦登实验室物理系）；Department of Physics, University of Warwick（华威大学物理系）；Physikalisches Institut, Goethe-Universität Frankfurt（法兰克福歌德大学物理研究所）；Laboratoire National des Champs Magnétiques Intenses, LNCMI-CNRS (UPR3228), EMFL, Univ. Grenoble Alpes, Univ. Toulouse, INSA-T（强磁场国家实验室，LNCMI-CNRS (UPR3228)，欧洲强磁场联合实验室，格勒诺布尔阿尔卑斯大学，图卢兹大学，INSA-T）；Max-Planck-Institute for So（马克斯·普朗克研究所）
Skyrmions are small magnetic quasiparticles, which are uniquely characterized by their topological charge and their helicity. In this Rapid Communication, we show via calculations how both properties can be determined without relying on real-space imaging. The orbital magnetization and topological Hall conductivity measure the arising magnetization due to the circulation of electrons in the bulk and the occurrence of topologically protected edge channels due to the emergent field of a skyrmion crystal. Both observables quantify the topological Hall effect and distinguish skyrmions from antisky…
The electrical and magnetic response to a bias current has been investigated in a singlecrystalline ferromagnetic manganese oxide $\Pr_{0.8}$Ca$_{0.2}$MnO$_3$ . A significant decrease of the magnetization is observed at the same threshold current where a non-linearity of V-I characteristics appears. Such a behavior cannot be understood in the framework of the filamentary picture usually invoked for the non linearity of the other manganese oxides. Instead, an analogy with spintronic features might be useful and experimental signatures seem to be in agreement with excitations of spin waves by an…
We report on high-resolution dc-magnetization (M) measurements on a high-quality single crystal of YbCo2Si2. M was measured down to 0.05K and in fields up to 4T, with the magnetic field oriented along the crystallographic directions [100], [110] and [001] of the tetragonal structure.
We study S=1 kagome antiferromagnets with isotropic Heisenberg exchange $J$ and strong easy axis single-ion anisotropy $D$. For $D \gg J$, the low-energy physics can be described by an effective $S=1/2$ $XXZ$ model with antiferromagnetic $J_z \sim J$ and ferromagnetic $J_\perp \sim J^2/D$. Exploiting this connection, we argue that non-trivial ordering into a "spin-nematic" occurs whenever $D$ dominates over $J$, and discuss its experimental signatures. We also study a magnetic field induced transition to a magnetization plateau state at magnetization 1/3 which breaks lattice translation symmet…
The magnetic behavior of the heavy fermion superconductor CeCoIn5 has been investigated. The low field magnetization data show flux jumps in the mixed state of the superconducting phase in a restricted range of temperature. These flux jumps begin to disappear below 1.7 K, and are completely absent at 1.5 K. The magnetization loops are asymmetric, suggesting that surface and geometrical factors dominate the pinning in this system. The lower critical field (Hc1), obtained from the magnetization data, shows a linear temperature dependence and is anisotropic. The calculated penetration depth is al…
The magnetization curve of the $(S,s)=(1,1/2)$ ferrimagnetic alternating spin chain with the single-ion anisotropy $D$ is investigated with the numerical exact diagonalization of finite clusters and size-scaling analyses. The system has a plateau at 1/3 of the saturation moment, which corresponds to the spontaneous magnetization for D=0. Varying $D$ in the 1/3-magnetized ground state under the external field along the axis of $D$, a quantum phase transition is revealed to occur at the critical value $D/J=1.114 \pm 0.001$ where the plateau vanishes. Except for the critical point, the plateau is…
We have investigated the in-plane uniaxial pressure effect on the antiferromagnetic Mott insulator Ca2RuO4 from resistivity and magnetization measurements. We succeeded in inducing the ferromagnetic metallic phase at lower critical pressure than by hydrostatic pressure, indicating that the flattening distortion of the RuO6 octahedra is more easily released under in-plane uniaxial pressure. We also found a striking in-plane anisotropy in the pressure responses of various magnetic phases: Although the magnetization increases monotonically with pressure diagonal to the orthorhombic principal axes…
Finite-temperature Drude weight (spin stiffness) D(T) is evaluated within the anisotropic spin-1/2 Heisenberg model on a chain using the exact diagonalization for small systems. It is shown that odd-side chains allow for more reliable scaling and results, in particular, if one takes into account corrections due to low-frequency finite-size anomalies. At high T and zero magnetization D is shown to scale to zero approaching the isotropic point Δ=1. On the other hand, for Δ>2 at all magnetizations D is nearly exhausted with the overlap with the conserved energy current. Results for the T variatio…
A spin-rotation-invariant Green's-function theory of long-range and short-range order (SRO) in the $S=1/2$ antiferromagnetic Heisenberg model with spatially anisotropic couplings on a simple cubic lattice is presented. The staggered magnetization, the two-spin correlation functions, the correlation leng spin-rotation-invariant Green's-function theory of long-range and short-range order (SRO) in the $S=1/2$ antiferromagnetic Heisenberg model with spatially anisotropic couplings on a simple cubic lattice is presented. The staggered magnetization, the two-spin correlation functions, the correlati…
We consider the effect of quantum spin fluctuations on the ground state properties of the Heisenberg antiferromagnet on an anisotropic triangular lattice using linear spin-wave theory. This model should describe the magnetic properties of the insulating phase of the kappa-(BEDT-TTF)_2 X family of superconducting molecular crystals. The ground state energy, the staggered magnetization, magnon excitation spectra and spin-wave velocities are computed as a function of the ratio between the second and first neighbours, J2/J1. We find that near J2/J1 = 0.5, i.e., in the region where the classical sp…
The exchange coupling at the interfaces of magnetic superlattices consisting of ferromagnetic $SrRuO_3$ and antiferromagnetic $SrMnO_3$ grown on (001) oriented $SrTiO_3$ is studied with in-plane and out-of-plane orientations, with respect to the substrate plane, of the cooling magnetic field. The magnetization of the in-plane, field cooled hysteresis loop is lower than the corresponding in-plane zero-field-cooled hysteresis loop. The out-of-plane field cooled hysteresis loop is shifted, from the origin, along the graphical magnetization axis. We attribute this irreversible rotation of the mome…
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 study finite-temperature magnetization transport in a one-dimensional anisotropic Heisenberg model, focusing in particular on the gapped phase. Using numerical simulations by two different methods, a propagation of localized wavepackets and a study of nonequilibrium steady states of a master equation in a linear-response regime, we conclude that the transport at finite temperatures is diffusive. With decreasing temperature the diffusion constant increases, possibly exponentially fast. This means that at low temperatures the transition from ballistic to asymptotic diffusive behavior happens …
We present a detailed study of RNi1-xBi2+-y (R = La-Nd, Sm, Gd-Dy) single crystals by measurements of stoichiometry and temperature dependent magnetic susceptibility, magnetization, and electrical resistivity. This series forms with partial Ni occupancy as well as a variable Bi occupancy. For R = Ce-Nd, Sm, Gd-Dy, the RNi1-xBi2+-y compounds show local-moment like behavior and order antiferromagnetically at low temperatures. Determination of anisotropies as well as antiferromagnetic ordering temperatures for RNi1-xBi2+-y (R = Ce-Nd, Sm, Gd-Dy) have been made. Although crystalline samples from t…
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 numerically investigate the critical behavior of the spin-(1,1/2) Heisenberg ferrimagnet with anisotropic exchange coupling in a magnetic field. A quantized magnetization plateau as a function of the field, appearing at a third of the saturated magnetization, is stable over whole the antiferromagnetic coupling region. The plateau vanishes in the ferromagnetic coupling region via the Kosterlitz-Thouless transition. Comparing the quantum and classical magnetization curves, we elucidate what are essential quantum effects.
Single crystals of EuNiGe$_3$ crystallizing in the non-centrosymmetric BaNiSn$_3$-type structure have been grown using In flux, enabling us to explore the anisotropic magnetic properties which was not possible with previously reported polycrystalline samples. The EuNiGe$_3$ single crystalline sample is found to order antiferromagnetically at 13.2 K as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M(H) is distinctly different for field parallel to ${ab}$-plane and $c$-axis; the ${ab}$-plane magnetization varies nearly…
The magnetization, crystal structure, and thermal expansion of a nearly stoichiometric Sr$_{1.04(3)}$Er$_{2.09(6)}$O$_{4.00(1)}$ single crystal have been studied by PPMS measurements and in-house and high-resolution synchrotron X-ray powder diffraction. No evidence was detected for any structural phase transitions even up to 500 K. The average thermal expansions of lattice constants and unit-cell volume are consistent with the first-order Grüneisen approximations taking into account only the phonon contributions for an insulator, displaying an anisotropic character along the crystallographic \…
We report a novel feature of the temperature induced magnetization jump observed along the a-axis of the GdVO3 single crystal at temperature TM = 0.8 K. Below TM, the compound shows no coercivity and remanent magnetization indicating a homogenous antiferromagnetic structure. However, we will demonstrate that the magnetic state below TM is indeed history dependent and it shows up in different jumps in the magnetization only when warming the sample through TM. Such a magnetic memory effect is highly unusual and suggesting different domain arrangements in the supposedly homogenous antiferromagnet…
SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured both the Hall effect and the magnetoresistance (MR) of the films as a function of the angle between the applied field and the normal to the films at temperatures above Tc. We extracted the extraordinary Hall effect that is proportional to the perpendicular component of the magnetization and thus the MR for each angle of the applied field could be correlated with the magnitude and orientation of the induced magnetization. We successfully fit t…
Specific heat and magnetization measurements have been carried out under a range of magnetic fields on single crystals of Ca3Co2O6. This compound is composed of Ising magnetic chains that are arranged on a triangular lattice. The intrachain and interchain couplings are ferromagnetic and antiferromagnetic, respectively. This situation gives rise to geometrical frustration, that bears some similarity to the classical problem of a two-dimensional Ising triangular antiferromagnet. This paper reports on the ordering process at low-T and the possibility of one-dimensional features at high-T.
We investigate the effect of mass anisotropy on the Wigner crystallization transition in a two-dimensional (2D) electron gas. The static and dynamical properties of a 2D Wigner crystal have been calculated for arbitrary 2D Bravais lattices in the presence of anisotropic mass, as may be obtainable in Si MOSFETs with (110) surface. By studying the stability of all possible lattices, we find significant change in the crystal structure and melting density of the electron lattice with the lowest ground state energy.
Non reciprocal spin waves have a chiral asymmetry so that their energy is different for two opposite wave vectors. They are found in atomically thin ferromagnetic overlayers with in plane magnetization and are linked to the anti-symmetric Dzyaloshinskii-Moriya surface exchange. We use an itinerant fermion theory based on first principles calculations to predict that non-reciprocal magnons can occur in Fe$_3$GeTe$_2$, the first stand alone metallic two dimensional crystal with off-plane magnetization. We find that both the energy and lifetime of magnons are non-reciprocal and we predict that ac…
Compounds with a Kagome type lattice are known to exhibit magnetic frustration. Large single crystals of two compounds Ni3V2O8 and Co3V2O8, which are variants of a Kagome net lattice, have been grown successfully by the floating zone technique using an optical image furnace. The single crystals are of high quality and exhibit intriguing magnetic properties.
We report that the major features in the temperature dependence of dc and ac magnetization of a well-known spin-chain compound, Ca3Co2O6, which has been known to exhibit two complex magnetic transitions due to geometrical frustration (one near 24 K and the other near 10 K), are found to be qualitatively unaffected in its nano form synthesized by high-energy ball-milling. However, the multiple steps in isothermal magnetization - a topic of current interest in low-dimensional systems - known for the bulk form well below 10 K is absent in the nano particles. We believe that this finding will be u…
We report the crystal growth by chemical vapor transport together with a thorough structural and magnetic characterization of the quasi-2D magnets (Fe$_{1-x}$Ni$_x$)$_2$P$_2$S$_6$ with $x_\textrm{Ni} = \textrm{0, 0.3, 0.5, 0.7, 0.9 & 1}$. As-grown crystals exhibit a layered morphology with weak van der Waals interactions between layers parallel to the crystallographic $ab$ plane of the monoclinic structure in the space group $C2/m$ (No. 12). Magnetization measurements reveal an antiferromagnetic ground state for all grown crystals. In the ordered state, the magnetization along different crysta…
Effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization ($M_L(χ)$) measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that $M_L(χ)$ in a superconductor with four-fold gap displays a four-fold oscillation reflecting the gap and Fermi surface anisotropies, and the sign of this oscillation changes at a field between $H_{c1}$ and $H_{c2}$. As a prototype of unconventional superconductors, magnetiz…
Detailed magnetization, specific heat, and $^7$Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyperhoneycomb Kitaev magnet $β$-Li$_2$IrO$_3$ are reported. At high temperatures, {\cred anisotropy of the magnetization is reflected by the different Curie-Weiss temperatures for different field directions}, in agreement with the combination of a ferromagnetic Kitaev interaction ($K$) and a negative off-diagonal anisotropy ($Γ$) as two leading terms in the spin Hamiltonian. At low temperatures, magnetic fields applied along $a$ or $c$ have only a weak effect on the system…
We have determined the temperature evolution of the spin and orbital moments in the zero magnetization ferromagnet Sm$_{1-x}$Gd$_x$Al$_2$ (x = 0.024) by combining polarized and unpolarized single crystal neutron diffraction data. The sensitivity of the polarized neutron technique has allowed the moment values to be determined with a precision of $\approx 0.1$~\mub. Our results clearly demonstrate that, when magnetised by a field of 8T, the spin and orbital moments in Sm$_{1-x}$Gd$_x$Al$_2$ are oppositely directed so that the net magnetization is very small. Below 60 K the contributions from sp…
Several diamond bulk crystals with a concentration of electrically neutral single substitutional nitrogen atoms of $\lesssim 80~$ppm, the so-called C- or P1-centres, were irradiated with electrons at 10 MeV energy and low fluence. The results show a complete suppression of the irreversible behavior in field and temperature of the magnetization below $\sim 30$~K, after a decrease of $\lesssim 40~$ppm in the concentration of C-centres produced by the electron irradiation. This result indicates that magnetic C-centres are at the origin of the large hysteretic behavior found recently in nitrogen-d…
Cobalt nanowires with a diameter in the range between 50 to 100nm can be prepared as single-crystal wires with the easy axis (the c-axis) perpendicular to the wire axis. The competition between the crystal anisotropy and demagnetization energy frustrates the magnetization direction. A periodic modulation of the angle between M and the wire axis yields a lower energy.
Magnetization and its relaxation have been measured in $Ba(Fe_{1-x}Co_x)_2As_2$ single crystals at various doping levels ranging fromvery underdoped to very overdoped regimes. Sizable magnetization relaxation rate has been observed in all samples, indicating a moderate vortex motion and relatively small characteristic pinning energy. Detailed analysis leads to the following conclusions: (1) A prominent second-peak (SP) effect was observed in the samples around the optimal doping level (x $\approx$ 0.08), but it becomes invisible or very weak in the very underdoped and overdoped samples; (2) Th…
We investigate the anisotropic nature of magnetocrystalline coupling between the crystallographic and skyrmion crystal (SKX) lattices in the chiral magnet MnSi by magnetic field-angle resolved resonant ultrasound spectroscopy. Abrupt changes are observed in the elastic moduli and attenuation when the magnetic field is parallel to the [011] crystallographic direction. These observations are interpreted in a phenomenological Ginzburg-Landau theory that identifies switching of the SKX orientation to be the result of an anisotropic magnetocrystalline coupling potential. Our paper sheds new light o…
