Magneto-optical study of metamagnetic transitions in the antiferromagnetic phase of $α$-RuCl$_3$
Julian Wagner, Anuja Sahasrabudhe, Rolf Versteeg, Lena Wysocki, Zhe Wang, Vladimir Tsurkan, Alois Loidl, Daniel. I. Khomskii, Hamoon Hedayat, Paul H. M. van Loosdrecht
$α$-RuCl$_3$ is a promising candidate material to realize the so far elusive quantum spin liquid ground state. However, at low temperatures, the coexistence of different exchange interactions couple the effective pseudospins into an antiferromagnetically zigzag (ZZ) ordered state. The low-field evolution of spin structure is still a matter of debate and the magnetic anisotropy within the honeycomb planes is an open and challenging question. Here, we investigate the evolution of the ZZ order parameter by second-order magneto-optical effects, the magnetic linear dichroism and magnetic linear birefringence. Our results clarify the presence and nature of metamagnetic transitions in the ZZ phase of $α$-RuCl$_3$. Our experimental observations show the presence of initial magnetic domain repopulation followed by a spin-flop transition for small in-plane applied magnetic fields ($\approx$ 1.6 T) along specific crystallographic directions. In addition, using a magneto-optical approach, we detected the recently reported emergence of a field-induced intermediate phase before suppressing the ZZ order. Our results disclose the details of various angle-dependent in-plane metamagnetic transitions quantifying the bond-anisotropic interactions present in $α$-RuCl$_3$
We present first-principles results on the magnetoelastic coupling in $α$-RuCl$_3$ and uncover a striking dependence of the magnetic coupling constants on strain effects. Different magnetic interactions are found to respond very unequally to variations in the lattice, with the Kitaev interaction being the most sensitive. Exact diagonalization results on our magnetoelastic model reproduce recent measurements of the structural Grüneisen parameter and explain the origin of the negative magnetostriction of $α$-RuCl$_3$, disentangling contributions related to different anisotropic interactions and …
We report magnetic and thermodynamic properties of single crystal $α$-RuCl$_3$, in which the Ru$^{3+}$ ($4d^5$) ion is in its low spin state and forms a honeycomb lattice. Two features are observed in both magnetic susceptibility and specific heat data; a sharp peak at 7~K and a broad hump near 10-15K. In addition, we observe a metamagnetic transition between 5~T and 10~T. Our neutron diffraction study of single crystal samples confirms that the low temperature peak in the specific heat is associated with a magnetic order with unit cell doubling along the honeycomb (100) direction, which is co…
The Kitaev material $α$-RuCl$_3$ is among the most prominent candidates to host a quantum spin-liquid state endowed with fractionalized excitations. Recent experimental and theoretical investigations have separately revealed the importance of both the magnetoelastic coupling and the magnetic anisotropy, in dependence of the applied magnetic field direction. In this combined theoretical and experimental research, we investigate the anisotropic magnetic and magnetoelastic properties for magnetic fields applied along the main crystallographic axes as well as for fields canted out of the honeycomb…
We discuss the implications that new magnetocaloric, thermal expansion and magnetostriction data in $α$-RuCl$_{3}$ single crystals have on its temperature-field phase diagram and uncover the magnetic-field dependence of an apparent energy gap structure $Δ(H)$ that evolves when the low temperature antiferromagnetic order is suppressed. We show that, depending on how the thermal expansion data is modeled, $Δ(H)$ can show a cubic field dependence and remain finite at zero field, consistent with the pure Kitaev model hosting itinerant Majorana fermions and localized $\mathbb{Z}_{2}$ fluxes. Our ma…
We report vibrating coil magnetometry of the spin ice system Ho2Ti2O7 down to ~0.04 K for magnetic fields up to 5 T applied parallel to the [111] axis. History dependent behavior emerges below T*_0 ~ 0.6 K near zero magnetic field, in common with other spin ice compounds. In large magnetic fields we observe a magnetization plateau followed by a hysteretic metamagnetic transition. The temperature dependence of the coercive fields as well as the susceptibility calculated from the magnetization identify the metamagnetic transition as a line of first order transitions terminating in a critical end…
Motivated by the possibility of an intermediate U(1) quantum spin liquid phase in out-of-plane magnetic fields and enhanced magnetic fluctuations in exfoliated α-RuCl3 flakes, we study magneto-Raman spectra of exfoliated multilayer α-RuCl3 in out-of-plane magnetic fields of -6 T to 6 T at temperatures of 670 mK - 4 K. While the literature currently suggests that bulk α-RuCl3 is in an antiferromagnetic zigzag phase with R3bar symmetry at low temperature, we do not observe R3bar symmetry in exfoliated α-RuCl3 at low temperatures. While we saw no magnetic field driven transitions, the Raman modes…
The metamagnetic transitions in single-crystal ErNi$_2$B$_2$C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields of the transitions depend crucially on the angle between applied field and the easy axis [100]. Torque measurements have been made while changing angular direction of the magnetic field (parallel to basal tetragonal $ab$-planes) in a wide angular range (more than two quadrants). Sequences of metamagnetic transitions with increasing field are found to be different for the magnetic field along (or close enough to) the easy [100] axis from that ne…
High-resolution thermal expansion and magnetostriction measurements were performed on single crystals of $α$-RuCl$_3$ in magnetic fields applied parallel to the Ru-Ru bonds. The length changes were measured in the direction perpendicular to the honeycomb planes. Our data show clear thermodynamic characteristics for the field-induced phase transition at the critical field $μ_0H_{c1} = 7.8(2)$ T where the antiferromagnetic zigzag order is suppressed. At higher fields, a kink in the magnetostriction coefficient signals an additional phase transition around $μ_0H_{c2} \approx 11$ T. The extracted …
We present a study of the magnetocaloric effect in La5/8-yPryCa3/8MnO3 (y=0.3) and Pr0.5Ca0.09Sr0.41MnO3 manganites. The low temperature state of both ystems is the result of a competition between the antiferromagnetic and ferromagnetic phases. The samples display magnetocaloric effect evidenced in an adiabatic temperature change during a metamagnetic transition from an antiferromagnetic to a ferromagnetic phase . As additional features, La5/8-yPryCa3/8MnO3 exhibits phase separation characterized by the coexistence of antiferromagnetic and ferromagnetic phases and Pr0.5Ca0.09Sr0.41MnO3 display…
The 2D layered insulator $α$-RuCl$_3$ is a candidate material for a quantum spin-liquid state, which may be realized when a magnetic field suppresses the antiferromagnetic order present at low temperature. Oscillations in the field dependence of the thermal conductivity, observed for an in-plane magnetic field $B$ up to a critical field $B^{\star}$, have been attributed to exotic charge-neutral fermions, viewed as evidence of a quantum spin-liquid state between the critical field $B_{c}$ $\simeq 7$ T at which the antiferromagnetic phase ends and $B^{\star}$. Here we report measurements of the …
The magnetoelastic coupling in Ca$_{1.8}$Sr$_{0.2}$RuO$_4$ and in Ca$_{1.5}$Sr$_{0.5}$RuO$_4$ has been studied combining high-resolution dilatometer and diffraction techniques. Both compounds exhibit strong anomalies in the thermal-expansion coefficient at zero and at high magnetic field as well as an exceptionally large magnetostriction. All these structural effects, which are strongest in Ca$_{1.8}$Sr$_{0.2}$RuO$_4$, point to a redistribution of electrons between the different $t_{2g}$ orbitals tuned by temperature and magnetic field. The temperature and the field dependence of the thermal-e…
Strong metamagnetic switching and anisotropic magnetotransport in the distorted kagome magnet Tb6Ti4Al43
Indian Institute of Technology Delhi（印度理工学院德里分校）；Max-Planck-Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Department of Physics, Institute for Materials Research, Tohoku University（东北大学物质材料研究学院物理学系）
Large magnetocaloric effect (MCE) and magnetoresistance (MR) together with negligible hysteresis loss has been observed in ErNiSi compound, which undergoes metamagnetic transition at low temperatures. Magnetization, heat capacity and resistivity measurements confirm the metamagnetic transition. The maximum value of isothermal entropy change and MR for a field change of 50 kOe are found to be 19.1 J/kg K and -34 %. Large MCE with negligible magnetic hysteresis loss could make this material promising for low temperature magnetic refrigeration.
Magnetoresistance and magnetocaloric properties of polycrystalline HoRhGe have been studied. This compound orders antiferromagnetically with a Neel temperature (TN) of 5.5 K and undergoes a first order metamagnetic transition at 2 K. It shows a large negative magnetoresistance of 25% at TN, for a field of 50 kOe. However, at 2 K and in lower fields, the magnetoresistance is found to be positive with a magnitude of about 12%, which is attributed to the first order metamagnetic transition. The compound also shows large magnetocaloric effect near its Neel temperature. Field dependence of magnetic…
The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at $T_{\mathrm{C}}=340$(1) K and a spin-reorientation transition at $T_{\mathrm{N}}=326$(1) K to an antiferromagnetic phase. First-principles electronic structure calculations indicate a not-fully polarized spin state of Mn in a $d^5$ electron configuration with $J=S=3$/2, in agreement with the saturation magnetization of 3~$μ_{\mathrm{B}}$ in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous…
We report on the observation of large, step-like anomalies in the magnetization ($ΔM = 0.74$\,$μ_{\rm B}$/Ce), in the magnetostriction ($Δl/l_{0} = 2.0 \cdot 10^{-3}$), and in the magnetoresistance in polycrystals of the paramagnetic heavy-fermion system CeTiGe at a critical magnetic field $μ_0 H_c \approx $ 12.5\,T at low temperatures. The size of these anomalies is much larger than those reported for the prototypical heavy-fermion metamagnet CeRu$_2$Si$_2$. Furthermore, hysteresis between increasing and decreasing field data indicate a real thermodynamic, first-order type of phase transition…
Magnetic-field effect on the magnetic and electric properties in a chiral polar ordered corundum Ni$_2$InSbO$_6$ has been investigated. Single-crystal soft x-ray and neutron diffraction measurements confirm long-wavelength magnetic modulation. The modulation direction tends to align along the magnetic field applied perpendicular to the polar axis, suggesting that the nearly proper-screw type helicoid should be formed below 77\,K. The application of a high magnetic field causes a metamagnetic transition. In a magnetic field applied perpendicular to the polar axis, a helix-to-canted antiferromag…
The metamagnetic transitions in single-crystal rare-earth nickel borocarbide HoNi_{2}B_{2}C and ErNi_{2}B_{2}C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields of the transitions depend crucially on the angle between applied field and the easy axis [110] for HoNi_2B_2C and [100] for ErNi_2B_2C. Torque measurements have been made while changing angular direction of the magnetic field (parallel to basal tetragonal ab-planes) in a wide angular range (more than two quadrants). The results are used not only to check and refine the angular diagram for metamag…
We present new, high resolution Hall effect and magnetoresistance measurements across the metamagnetic transition in the heavy fermion compound CeRu2Si2. The results force us to rethink the notion that the transition is accompanied by an abrupt f-electron localisation. Instead, we explain our data assuming a continuous change of the Fermi surface. We also point out ambiguities in the interpretation of dHvA data and give a possible solution to the problem of the "missing mass".
We have studied the ultrasonic velocity and ac susceptibility of $URu_2Si_2$ in d. c. magnetic fields up to 45T. A significant difference between the constructed H-T phase diagram and that extracted from earlier pulsed fields measurements can be explained in terms of a large magnetocaloric effect. A hysteresis of metamagnetic transition at low temperatures and a new phase separation line have been observed for the first time.
Metamagnetism in layered ruthenates has been interpreted as a novel kind of quantum critical behavior. In an external magnetic field, Ca$_{2-x}$Sr$_x$RuO$_4$ undergoes a metamagnetic transition accompanied by a pronounced magnetostriction effect. In this paper we present a mean-field study for a microscopic model that naturally reproduces the key features of this system. The phase diagram calculated is equivalent to the experimental $T$-$x$ phase diagram. The presented model also gives a good basis to discuss the critical metamagnetic behavior measured in the system.
Electrical resistivity ($ρ$), magnetoresistance (MR), magnetization, thermopower and Hall effect measurements on the single crystal Gd$_{2}$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure are reported. The well-defined minimum in $ρ$ at a temperature above Néel temperature (T$_N$= 21 K) and large negative MR below $\sim$ 3T$_N$, reported earlier for the polycrystals, are reproducible even in single crystals. Such features are generally uncharacteristic of Gd alloys. In addition, we also found interesting features in other data, e.g., two-step first-order-like metamagnetic tra…
The link between the metamagnetic transition and novel spin-triplet superconductivity of UTe$_2$ was discussed thermodynamically through magnetostriction measurements in a pulsed-magnetic field. We revealed a discontinuous magnetostriction across the metamagnetic transition at $μ_0H_{\rm m}\approx 35$~T for the applied magnetic fields along the crystallographic $b$ axis in the orthorhombic structure. The resultanting volume magnetostriction of $ΔV/V \approx-5.9\times 10^{-4}$ gives the initial pressure dependence of $H_{\rm m}$ by employing the Clausius-Clapeyron's equation, which agrees with …
In this paper, the magnetic and transport properties were systematically studied for EuAg$_4$As$_2$ single crystals, crystallizing in a centrosymmetric trigonal CaCu$_4$P$_2$ type structure. It was confirmed that two magnetic transitions occur at $\textit{T}$$_{N1}$ = 10 K and $\textit{T}$$_{N2}$ = 15 K, respectively. With the increasing field, the two transitions are noticeably driven to lower temperature. At low temperatures, applying a magnetic field in the $\textit{ab}$ plane induces two successive metamagnetic transitions. For both $\textit{H}$ $\parallel$ $\textit{ab}$ and $\textit{H}$ $…
We present time-resolved magneto-optical spectroscopy on the magnetic Mott-Hubbard-insulating Kitaev spin liquid candidate $α$-RuCl$_3$ to investigate the nonequilibrium dynamics of its antiferromagnetically ordered zigzag groundstate after photoexcitation. A systematic study of the transient magnetic linear dichroism under different experimental conditions (temperature, external magnetic field, photoexcitation density) gives direct access to the dynamical interplay of charge excitations with the zigzag ordered state on ultrashort time scales. We observe a rather slow initial demagnetization (…
The honeycomb Kitaev model in a magnetic field is a source of a topological quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. We present experimental results for the thermal Hall effect of the material $α$-RuCl$_{3}$ which recently emerged as a prime candidate for realizing such physics. At temperatures above long-range magnetic ordering $T\gtrsim T_N\approx8$ K, we observe with an applied magnetic field $B$ perpendicular to the honeycomb layers a sizeable positive transversal heat conductivity $κ_{xy}$ which increases linearly with $B$. Upon r…
A caged compound CeOs2Al10, crystallizing in the orthorhombic YbFe2Al10-type structure, undergoes a mysterious phase transition at T_0=29 K. We report the results of electron diffraction, magnetization, and magnetoresistance for single crystals. Superlattice reflections characterized by a wave vector q = (0, -2/3, 2/3) observed at 15 K indicate a structural modification in the ordered state. Activation-type behavior of the electrical resistivity along the three principal axes below 50 K suggests gap opening in the conduction band. The magnetic susceptibility χ= M/B is highly anisotropic, χ_a>χ…
Metamagnetic transitions in single-crystal rare-earth nickel borocarbide HoNi$_2$B$_2$C have been studied at T\approx 1.9 K with a Quantum Design torque magnetometer. This compound is highly anisotropic with a variety of metamagnetic states at low temperature which includes antiferromagnetic, ferrimagnetic, non-collinear and ferromagnetic-like (saturated paramagnet) states. The critical fields of the transitions depend crucially on the angle $θ$ between applied field and the easy axis [110]. Measurements of torque along the c-axis have been made while changing the angular direction of the magn…
The 6H-perovskites Ba$_3$RRu$_2$O$_9$ (R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of $4d - 4f$ magnetic interactions. Here, we have reported a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba$_3$GdRu$_2$O$_9$. The signature of long-range antiferromagnetic (AFM) ordering $\sim$ 14.8 K ($T_N$) is evident from the magnetization and heat capacity studies. The $T_N$ shifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magne…
We present out-of-plane dielectric and magnetodielectric measurements of single crystallines $α$-RuCl$_3$ with various degrees of stack faults. A frequency dependent, but field independent, dielectric anomaly appears at $T_{A}\:(f=100\:\mathrm{kHz})\sim$ 4 K once both magnetic transitions at $T_{N1}\sim$ 7 K and $T_{N2}\sim$ 14 K set in. The observed dielectric anomaly is attributed to the emergency of possible local electric polarizations whose inversion symmetry is broken by inhomogeneously distributed stacking faults. A field-induced intermediate phase is only observed when a magnetic field…
Metamagnetism in antiferromagnets exhibits distinct critical behaviors and dynamics when invoking spin reversal and rotation. Here we show a 0.05% anisotropic strain suffices to in-situ modulate the metamagnetic critical field of the Mott insulator Sr2IrO4 by over 50%, enabling electrical switching of the transition. Resonant x-ray scattering and model simulation reveal that the transition is completely tuned from the spin-flop to spin-flip type as the strain introduces C4-symmetry-breaking magnetic anisotropy. Simultaneous transport study indicates the metamagnetic responses are reflected in …
Triple-layered ruthenate Sr$_4$Ru$_3$O$_{10}$ shows a first-order itinerant metamagnetic transition for in-plane magnetic fields. Our experiments revealed rather surprising behavior in the low-temperature transport properties near this transition. The in-plane magnetoresistivity $ρ$$_{ab}$(H) exhibits ultrasharp steps as the magnetic field sweeps down through the transition. Temperature sweeps of $ρ$$_{ab}$ for fields within the transition regime show non-metallic behavior in the up-sweep cycle of magnetic field, but show a significant drop in the down-sweep cycle. These observations indicate …
Material realization of the non-Abelian Kitaev spin liquid phase - an example of Ising topological order (ITO) - has been the subject of intense research in recent years. The $4d$ honeycomb Mott insulator $α$-RuCl$_3$ has emerged as a leading candidate, as it enters a field-induced magnetically disordered state where a half-integer quantized thermal Hall conductivity $κ_{xy}$ was reported. Further, a recent report of a sign change in the quantized $κ_{xy}$ across a certain crystallographic direction is strong evidence for a topological phase transition between two ITOs with opposite Chern numb…
An external magnetic field can induce a transition in $α$-RuCl$_3$ from an ordered zigzag state to a disordered state that is possibly related to the Kitaev quantum spin liquid. Here we present new field dependent inelastic neutron scattering and magnetocaloric effect measurements implying the existence of an additional transition out of the quantum spin liquid phase at an upper field limit $B_u$. The neutron scattering shows three distinct regimes of magnetic response. In the low field ordered state the response shows magnon peaks; the intermediate field regime shows only continuum scattering…
Here we report the observation of pressure-induced melting of antiferromagnetic (AFM) order and emergence of a new quantum state in the honeycomb-lattice halide alpha-RuCl3, a candidate compound in the proximity of quantum spin liquid state. Our high-pressure heat capacity measurements demonstrate that the AFM order smoothly melts away at a critical pressure (Pc) of 0.7 GPa. Intriguingly, the AFM transition temperature displays an increase upon applying pressure below the Pc, in stark contrast to usual phase diagrams, for example in pressurized parent compounds of unconventional superconductor…
We report an electrical transport study in Ca$_{2-x}$Sr$_{x}$RuO$_4$ single crystals at high magnetic fields ($B$). For $x =0.2$, the Hall constant $R_{xy}$ decreases sharply at an anisotropic metamagnetic (MM) transition reaching its value for Sr$_2$RuO$_4$ at high fields. A sharp decrease in the $A$ coefficient of the resistivity $T^2$-term and a change in the structure of the angular magnetoresistance oscillations (AMRO) for $B$ rotating in the planes, confirms the reconstruction of the Fermi surface (FS). Our observations and LDA calculations indicate a strong dependence of the FS on the C…
SSMO50 thin films were deposited by DC magnetron sputtering on LAO and STO substrates. The film on LAO is under compressive strain, while the film on STO is under tensile strain. All the magnetic and magnetotransport properties have been discussed in terms of strain controlled metamagnetic state.
We use high-resolution capacitive dilatometry to study the low-temperature linear magnetostriction of the bilayer ruthenate Sr$_3$Ru$_2$O$_7$ as a function of magnetic field applied perpendicular to the ruthenium-oxide planes ($B\parallel c$). The relative length change $ΔL(B)/L$ is detected either parallel or perpendicular to the c-axis close to the metamagnetic region near B=8 T. In both cases, clear peaks in the coefficient $λ(B)=d(ΔL/L)/dB$ at three subsequent metamagnetic transitions are observed. For $ΔL\perp c$, the third transition at 8.1 T bifurcates at temperatures below 0.5 K. This …
We have investigated the temperature and magnetic field dependence of magnetization ($M$), specific heat ($C_p$), and relative sample length change ($ΔL/L_0$) for understanding the field-induced metamagnetic transitions in quasi-one-dimensional monoclinic ($α$ phase) and triclinic ($γ$ phase) CoV$_2$O$_6$ spin chains. With the application of external magnetic field, a sharp peak emerges in $C_p$($T$) below $T_N$$=$15 K in $α$ phase and a hump-like feature appears above $T_N$$=$6.5 K in $γ$ phase due to the field-induced ferrimagnetic and ferromagnetic transitions, respectively. Strong field de…
Critical thermodynamics close to a metamagnetic quantum critical endpoint (QCEP) in a metal is discussed within the framework of spin-fluctuation theory. We analyze the effective potential for the Ising order parameter that is renormalized by spin-fluctuations and acquires a characteristic temperature dependence. The resulting magnetic field, H, and temperature, T, dependence of the magnetization, specific heat, thermal expansion, magnetostriction, susceptibility and the Grüneisen parameter are determined, and the crossover lines in the (H,T) phase diagram are specified. We point out that the …
We report detailed investigation of quantum oscillations in Sr3Ru2O7, observed inductively (the de Haas-van Alphen effect) and thermally (the magnetocaloric effect). Working at fields from 3 T to 18 T allowed us to straddle the metamagnetic transition region and probe the low- and high-field Fermi liquids. The observed frequencies are strongly field-dependent in the vicinity of the metamagnetic transition, and there is evidence for magnetic breakdown. We also present the results of a comprehensive rotation study. The most surprising result concerns the field dependence of the measured quasipar…
We report a novel negative magnetocaloric effect in CoMnSi_{1-x}Ge_{x} arising from a metamagnetic magnetoelastic transition. The effect is of relevance to magnetic refrigeration over a wide range of temperature, including room temperature. In addition we report a very high shift in the metamagnetic transition temperature with applied magnetic field. This is driven by competition between antiferromagnetic and ferromagnetic order which can be readily tuned by applied pressure and compositional changes.
We present a study of the upper critical field of the newly discovered heavy fermion superconductor UTe$_2$ by magnetoresistivity measurements in pulsed magnetic fields up to 60~T and static magnetic fields up to 35~T. We show that superconductivity survives up to the metamagnetic transition at $H_{\rm m} \approx 35$~T at low temperature. Above $H_{\rm m}$ superconductivity is suppressed. At higher temperature superconductivity is enhanced under magnetic field leading to reentrance of superconductivity or an almost temperature independent increase of $H_{\rm c2}$. By studying the angular depen…
We consider the exchange couplings present in an effective Hamiltonian of $α$-RuCl$_3$, known as the K-$Γ$ model. This material has a honeycomb lattice, and is expected to be a representative of the Kitaev materials (which can realize the 2d Kitaev model). However, the behaviour of RuCl$_3$ shows that the exchange interactions of the material are not purely Kitaev-like, especially because it has an antiferromagnetic ordering at low temperatures and under low strengths of an externally applied magnetic field. Fitting the data obtained from the measurements of the magnetotropic coefficient (the …
A very strong magnetoelastic effect in the CeCo$_{1-x}$Fe$_{x}$Si alloys is reported. The strength of the magnetostrictive effect can be tuned upon changing $x$. The moderate low-temperature linear magnetostriction observed at low Fe concentrations becomes very large ($\frac {ΔL}{L} \left(16 T,2 K\right) =$ 3$\times$10$^{-3}$) around the critical concentration ($x_c \approx$ 0.23) at which the long-range antiferromagnetic order vanishes. Upon increasing doping through the non-magnetic region ($x > x_c$), the magnetostriction strength gradually weakens again. Remarkably the low-temperature magn…
We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV$_{2}$O$_{6}$ by magnetization and heat capacity measurements. Both monoclinic $α$-CoV$_{2}$O$_{6}$ and triclinic $γ$-CoV$_{2}$O$_{6}$ exhibit field-induced metamagnetic transition from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to this field-induced metamagnetic transition, these systems show large conventional as well as inverse magnetocaloric effects. In $α$-CoV$_{2}$O$_{6}$, we observe field-induced complex magnet…
Understanding the nature of field-tuned metamagnetic quantum criticality in the ruthenate Sr3Ru2O7 has presented a significant challenge within condensed matter physics. It is known from experiments that the entropy within the ordered phase forms a peak, and is unexpectedly higher than that outside, while the magnetoresistivity experiences steep jumps near the ordered phase. We find a challenging connection between Sr3Ru2O7 and heavy-fermion metals expressing universal physics that transcends microscopic details. Our construction of the T-B phase diagram of Sr3Ru2O7 permits us to explain main …
Polycrystalline HoSn1.1Ge0.9 and DySn1.1Ge0.9 compounds have been studied by means of different experimental probes. Both the compounds are antiferromagnetic and show metamagnetic transition at low temperatures. HoSn1.1Ge0.9 shows a sign change in magnetocaloric effect (MCE) and magnetoresistance (MR) with field, which is attributed to the metamagnetic transition. DySn1.1Ge0.9 shows characteristics of a typical antiferromagnet, as evidenced by magnetization, MCE and MR data. 119Sn Mössbauer studies show hyperfine splitting at low temperatures, consistent with magnetization data. Thermoelectric…
The antiferromagnetic ground state and the metamagnetic transition to the ferromagnetic state of CsCl-ordered FeRh epilayers have been characterized using Hall and magnetoresistance measure- ments. On cooling into the ground state, the metamagnetic transition is found to coincide with a suppression in carrier density of at least an order of magnitude below the typical metallic level shown by the ferromagnetic state. The data reveal that this sub-metallic density of electron-like majority carriers in the antiferromagnetic phase are attributable to intrinsic doping from Fe/Rh substitution defect…
Layered α-RuCl3 is a promising material to potentially realize the long-sought Kitaev quantum spin liquid with fractionalized excitations. While evidence of this exotic state has been reported under a modest in-plane magnetic field, such behavior is largely inconsistent with theoretical expectations of Kitaev phases emerging only in out-of-plane fields. These predicted field-induced states have been mostly out of reach due to the strong easy-plane anisotropy of bulk crystals, however. We use a combination of tunneling spectroscopy, magnetotransport, electron diffraction, and ab initio calculat…
We report the measurements of anisotropic magnetization and magnetoresistance on single crystals of EuFe$_2$As$_2$, a parent compound of ferro-arsenide high-temperature superconductor. Apart from the antiferromagnetic (AFM) spin-density-wave transition at 186 K associated with Fe moments, the compound undergoes another magnetic phase transition at 19 K due to AFM ordering of Eu$^{2+}$ spins ($J=S=7/2$). The latter AFM state exhibits metamagnetic transition under magnetic fields. Upon applying magnetic field with $H\parallel c$ at 2 K, the magnetization increases linearly to 7.0 $μ_{B}$/f.u. at…
The pursuit of quantum spin liquid (QSL) in the Kitaev honeycomb magnets has drawn intensive attention recently. In particular, $α$-RuCl$_3$ has been widely recognized as a promising candidate for the Kitaev QSL. Although the compound exhibits an antiferromagnetic order under zero field, it is believed to be endowed with fractionalized excitations, and can be driven to the QSL phase by magnetic fields. Here, based on a realistic $K$-$J$-$Γ$-$Γ'$ model for $α$-RuCl$_3$ [1], we exploit the exponential tensor renormalization group approach to explore the phase diagram of the compound under magnet…
In pulsed magnetic fields up to 65T and at temperatures below the Néel transition, our magnetization and magnetostriction measurements reveal a field-induced metamagnetic-like transition that is suggestive of an antiferromagnetic to polarized paramagnetic or ferrimagnetic ordering. Our data also suggests a change in the nature of this metamagnetic-like transition from second- to first-order-like near a tricritical point at T_{tc} ~145K and H_{c}~52T. At high fields for H>H_{c} we found a decreased magnetic moment roughly half of the moment reported in low field measurements. We propose that \m…
The magnetic $H$-$T$ phase diagram and magnetocaloric effect in the recently discovered high-temperature heavy-fermion compound YbCoC$_2$ have been studied. With the increase in the external magnetic field YbCoC$_2$ experiences the metamagnetic transition and then transition to the ferromagnetic state. The dependencies of magnetic entropy change -$ΔS_m (T)$ have segments with positive and negative magnetocaloric effects for $ΔH \leq 6$~T. For $ΔH = 9$~T magnetocaloric effect becomes positive with a maximum value of -$ΔS_m (T)$ is 4.1 J / kg K and a refrigerant capacity is 56.6 J / kg.
