Dc Susceptibility Research Articles

Unusual spin dynamics in the van der Waals antiferromagnet FeGa2S4

Spin dynamics in the van der Waals antiferromagnet FeGa2S4with triangular lattices are investigated using magnetometry, neutron scattering, and muon spin relaxation measurements. The characteristic spin relaxation time is thoroughly clarified over thirteen orders of magnitude. Although the temperature dependence of DC and AC susceptibilities recalls a conventional spin-glass transition, nonlinear susceptibilities showing no divergences at the anomalous temperature,T∗=16.87(7) K, deny that and instead hint at other mechanisms. Elastic neutron scattering together with previously measured muon results depict a slowly fluctuated (∼10-5 s) spin state aboveT∗. In juxtaposing the underlying simplest structure among frustrated magnets with an intricate hierarchy of time scales, FeGa2S4can be a playground for studying temporal spin correlations in the two-dimensional limit.

Influence of Sr doping on the structural and magnetic properties of (Y,Gd)Ba[formula omitted]Sr[formula omitted]CuFeO[formula omitted] ([formula omitted]) studied by FTIR and 57Fe Mössbauer spectroscopy

The effect of replacing Y by Gd and Ba by Sr in YBaCuFeO5 is studied by Fourier Transform Infrared spectroscopy, 57Fe Mössbauer spectroscopy and DC susceptibility measurements. Site disorder is inferred from FTIR and Mössbauer spectra using a Maximum-Entropy-Method. A doping dependence of the IR peaks and the hyperfine parameters is explained in terms of bonding energies and electric field gradient variations in the crystal lattice caused by Fe/Cu site disorder. We find an influence of doping on the structural and magnetic properties through a correlation of hyperfine parameters such as the electric quadrupole splitting and the magnetic hyperfine field. We also find that a paramagnetic volume fraction appears for GdBaCuFeO5 that increases upon Sr doping at the Ba site. The different behavior of the susceptibility upon replacing Y by Gd is attributed to the lack of a favorable environment to enable a Gd-Fe or Gd-Cu exchange interaction.

Disordered magnetic ground state in a quasi-1-D d4columnar iridate Sr3LiIrO6.

Spin-orbit coupling (SOC) offers a large variety of novel and extraordinary magnetic and electronic properties in otherwise 'ordinary pool' of heavy ion oxides. Here we present a detailed study on an apparently isolated hexagonal 2Hspin-chain d4iridate Sr3LiIrO6(SLIO) with geometric frustration. Our structural studies reveal Li-Ir chemical order with desired stoichiometry in this compound, while x-ray absorption together with x-ray photoemission spectroscopic characterizations establish pure 5+ valence of Ir. We have established a magnetic ground state with finite Ir5+magnetic moments in this compound, contrary to the anticipated nonmagnetic Jeff= 0 state, through combined dc susceptibility,7Li nuclear magnetic resonance (NMR), muon spin relaxation (μSR) and ab-initio electronic structure studies. These investigations together with ac magnetic susceptibility and specific heat measurements reveal that despite having noticeable antiferromagnetic correlation among the Ir5+local moments, this system does not magnetically order down to at least 0.05 K, possibly due to geometrical exchange frustration, arising from the comparable nearest- and next-nearest-neighbor interchain Ir-O-O-Ir superexchange interaction strengths with opposite signs. However, the zero-field (ZF) μSR analysis shows emergence of a considerable proportion of spin-freezing on top of a spin-fluctuating dynamic magnetic background down to the lowest measured
temperature of 1.7 K, possibly due to some inhomogeneity and/or the much stronger intra-column Ir-Ir magnetic exchange interaction
strength relative to the inter-column Ir-Ir ones. The linear temperature dependence of the magnetic specific heat (Cm) in both zero and applied magnetic fields, plus the power-law behavior of the NMR spin-lattice relaxation rate suggest a gapless spinon density of states in this charge gapped disordered magnetic ground state of Sr3LiIrO6.

Quantifying variations associated with dental caries reveals disparity in effect allele frequencies across diverse populations

BackgroundDental caries (DC) is a multifaceted oral condition influenced by genetic and environmental factors. Recent advancements in genotyping and sequencing technologies, such as Genome-Wide Association Studies (GWAS) have helped researchers to identify numerous genetic variants associated with DC, but their prevalence and significance across diverse global populations remain poorly understood as most of the studies were conducted in European populations, and very few were conducted in Asians specifically in Indians.AimThis study aimed to evaluate the genetic affinity of effect alleles associated with DC to understand the genetic relationship between global populations with respect to the Indian context.MethodologyThis present study used an empirical approach in which variants associated with DC susceptibility were selected. These variants were identified and annotated using the GWAS summary. The genetic affinity was evaluated using Fst.ResultsThe effect of allele frequencies among different populations was examined, revealing variations in allele distribution. African populations exhibited higher frequencies of specific risk alleles, whereas East Asian and European populations displayed distinct profiles. South Asian populations showed a unique genetic cluster.ConclusionOur study emphasises the complex genetic landscape of DC and highlights the need for population-specific research as well as validation of GWAS-identified markers in Indians before defining them as established candidate genes.

Griffiths phase like behaviour in CoCrVZ (Z = Al, Ga) Heusler alloys

We report here the studies of structural and magnetic properties of two equiatomic quaternary Heusler alloys CoCrVZ (Z = Al, Ga). Both the alloys crystallize in LiMgPdSn type crystal structure (space group #216) with B2 (CoCrVAl) and A2 (CoCrVGa) type anti-site disorder between elemental sites. Intended stoichiometry was confirmed from the compositional analysis. The temperature dependence of dc magnetic susceptibility and the low temperature moment values show a nearly compensating ferrimagnetic behaviour at low temperatures for both the alloys. The inverse of dc magnetic susceptibility starts to deviate from the Curie–Weiss law below 220 K and 164 K for the alloys containing Al and Ga respectively. The Arrott plots confirms the absence of long range order down to 2 K. Further analysis of the dc and ac susceptibility shows that the observed behaviour is due to the presence of Griffiths like phase in these alloys.

Magnetic properties and magnetocaloric effect of Ln = Dy, Tb carborane-based metal-organic frameworks.

We present the synthesis and magneto-thermal properties of carborane-based lanthanide metal-organic frameworks (MOFs) with the formula {[(Ln)3(mCB-L)4(NO3)(DMF)n]·Solv}, where Ln = Dy or Tb, characterized by dc and ac susceptibility, X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and heat capacity measurements. The MOF structure is formed by polymeric 1D chains of Ln ions with three different coordination environments (Ln1, Ln2, Ln3) running along the b-axis, linked by carborane-based linkers thus to provide a 3D structure. Static magnetic measurements reveal that these MOFs behave at low temperature as a system of S* = 1/2 Ising spins, weakly interacting ferromagnetically along the 1D polymeric chain (J*/kB = +0.45 K (+0.5 K) interaction constant estimated for Dy-MOF (Tb-MOF)) and coupled to Ln ions in adjacent chains through dipolar antiferromagnetic interactions. The Dy MOF exhibits slow relaxation of magnetization through a thermally activated process, transitioning to quantum tunneling of the magnetization at low temperatures, while both compounds exhibit field-induced relaxation through a very slow, direct process. The maximum magnetic entropy changes (-ΔSmaxm) for an applied magnetic field change of 2-0 T are 5.71 J kg-1 K-1 and 4.78 J kg-1 K-1, for Dy and Tb MOFs, respectively, while the magnetocaloric effect (MCE) peak for both occurs at T ∼ 1.6 K, approximately double that for the Gd counterpart.

Phase transitions and slow spin dynamics of slightly inverted A-site spinel CoAl2−x Ga x O4

We report the properties of an A-site spinel magnet, CoAl2−x Ga x O4, and analyze its anomalous, low-temperature magnetic behavior, which is derived from inherent, magnetically frustrated interactions. Rietveld analysis of the x-ray diffraction profile for CoAl2−x Ga x O4 revealed that the metallic ions were randomly distributed in the tetrahedral (A-) and octahedral (B-) sites in the cubic spinel structure. The inversion parameter η could be controlled by varying the gallium (Ga) composition in the range 0.055 ⩽ η ⩽ 0.664. The composition-induced Néel-to-spin-glass (NSG) transition occurred between 0.05 ⩽ η ⩽ 0.08 and was verified by measurements of DC-AC susceptibilities χ and thermoremanent magnetization (TRM) below the Néel transition temperature T N. The relaxation rate and derivative with respect to temperature of TRM increased at both T N and the spin glass (SG) transition temperature T SG. The TRM decayed rapidly above and below these transitions. TRM was highly sensitive to macroscopic magnetic transitions that occurred in both the Néel and SG phases of CoAl2−x Ga x O4. In the vicinity of the NSG boundary, there was a maximum of the TRM relaxation rate at T max < T N. With increasing inversion η(x), the anomaly at T max merged with that of the Néel transition at a tricritical point (η tc, T tc) = (0.08, 4.0 K), where the paramagnetic, Néel, and SG states met. We successfully extracted the relaxation time τ and other characteristic parameters from the TRM isothermal temporal evolution based on the Weron function derived for a purely stochastic process. To distinguish the magnetic states, we compared our results with previously studied inversion-free A-site spinel, CoRh2O4, and CoGa2O4 cluster glass. We generated an inversion-temperature phase diagram based on the comprehensive measurements of DC and AC susceptibilities, TRM, and specific heat in the range 0.055 ⩽ η ⩽ 0.664 for CoAl2−x Ga x O4. Based on this phase diagram, we speculate that a NSG quantum critical phase transition occurred at η = 0.050(6). Our findings are consistent with suppression of the long-range order antiferromagnetic state in CoAl2O4 revealed through neutron diffraction studies, even at T << T N.

Haldane topological spin-1 chains in a planar metal-organic framework

Haldane topological materials contain unique antiferromagnetic chains with symmetry-protected energy gaps. Such materials have potential applications in spintronics and future quantum computers. Haldane topological solids typically consist of spin-1 chains embedded in extended three-dimensional (3D) crystal structures. Here, we demonstrate that [Ni(μ−4,4′-bipyridine)(μ-oxalate)]n (NiBO) instead adopts a two-dimensional (2D) metal-organic framework (MOF) structure of Ni2+ spin-1 chains weakly linked by 4,4′-bipyridine. NiBO exhibits Haldane topological properties with a gap between the singlet ground state and the triplet excited state. The latter is split by weak axial and rhombic anisotropies. Several experimental probes, including single-crystal X-ray diffraction, variable-temperature powder neutron diffraction (VT-PND), VT inelastic neutron scattering (VT-INS), DC susceptibility and specific heat measurements, high-field electron spin resonance, and unbiased quantum Monte Carlo simulations, provide a detailed, comprehensive characterization of NiBO. Vibrational (also known as phonon) properties of NiBO have been probed by INS and density-functional theory (DFT) calculations, indicating the absence of phonons near magnetic excitations in NiBO, suppressing spin-phonon coupling. The work here demonstrates that NiBO is indeed a rare 2D-MOF Haldane topological material.

Spin-liquid state with precursor ferromagnetic clusters interacting antiferromagnetically in frustrated glassy tetragonal spinel Zn0.8Cu0.2FeMnO4

Spinels (AB 2O4) with magnetic ions occupying only the octahedral B sites have inherent magnetic frustration which inhibits magnetic long-range order (LRO) but may lead to exotic states. Here we report on the magnetic properties of the tetragonal spinel Zn0.8Cu0.2FeMnO4, the tetragonality resulting from the Jahn–Teller active Mn3+ ions. X-ray diffraction and x-ray photoelectron spectroscopy of the sample yielded the composition () A [] B O4‒δ . Analysis of the temperature dependence of magnetization (M), ac magnetic susceptibilities (χ′ and χ′′), dc susceptibility (χ), heat capacity Cp , and neutron diffraction (ND) measurements show complex temperature-dependent short-range order (SRO) but without LRO. The data of χ vs. T fits the Curie–Weiss law: χ = C/(T ‒ θ) from T = 250 K to 400 K with θ ≃ 185 K signifying dominant ferromagnetic (FM) coupling with the FM exchange constant J/k B = 17 K, and C = 3.29 emu K mol‒1 Oe‒1 yielding an effective magnetic moment µ eff = 5.13 µ B resulting from the high-spin states of Cu2+ (A site) and Fe2+ (B site), while the B site trivalent ions Mn3+ and Fe3+ are in their low-spin states. The extrapolated saturation magnetization obtained from the M vs. H data at T = 2 K is explained using the spin arrangement (Cu2+↓) A [Fe2+↑, Fe3+↓, Mn3+↑] B leading to FM clusters interact antiferromagnetically at low temperatures. Temperature dependence of d(χT)/dT shows the onset of ferrimagnetism below ∼100 K and peaks near 47 K and 24 K. The relaxation time τ obtained from temperature and frequency dependence of χ″ when fit to the power law and Vogel–Fulcher laws confirm the cluster spin-glass (SG) state. The magnetic field dependence of the SG temperature follows the equation: with T SG (0) = 46.6 K, A = 8.6 × 10‒3 Oe‒0.593 and = 3.37. The temperature dependence of hysteresis loops yields coercivity HC ∼ 3.8 kOe at 2 K without exchange-bias, but HC decreases with increase in T becoming zero above 24 K, the T SG(H) for H = 800 Oe. Variations of Cp vs. T from 2 K to 200 K in H = 0 and H = 90 kOe do not show any peak characteristic of LRO. However, after correcting for the lattice contribution, a broad weak peak typically of SRO becomes evident centered around 40 K. For T < 9 K, Cp varies as T2 ; a typical signature of spin-liquids (SLs). Comparison of the ND measurements at 1.7 K and 79.4 K shows absence of LRO. Time dependence of thermo-remanent magnetization M TRM(t) studies below 9 K reveal weakening of the inter-cluster interaction with increase in temperature. A summary of these results is that in Zn0.8Cu0.2FeMnO4, ferromagnetic clusters interact antiferromagnetically without LRO but producing a cluster SG state at T SG(0) = 46.6 K, followed by SL behavior below 9 K.

Complex magnetic ordering behavior in the frustrated perovskite Ba2MnMoO6

New and exotic ground states of magnetic materials are highly sought after and are extensively studied for the insights they provide into the thermodynamics of disorder and fundamental magnetic interactions. By controlling the crystal structure of an appropriate magnetic lattice, it is possible to cause the strong magnetic exchange interactions to sum to zero and so be frustrated. Due to the presence of this frustration, the lowest energy configuration that results may be crucially dependent on the tiniest of energy differences between a multitude of states that have (almost) the same energy. The keen interest in these materials arises from the fact that these finely balanced systems offer a way of probing classical or quantum mechanical interactions that are of fundamental importance but are too weak to be observed in non-frustrated systems. Here, we combine local and crystallographic probes of the cation-ordered double perovskite Ba2MnMoO6 that contains a face-centered cubic lattice of S = 5/2 Mn2+ cations. Neutron diffraction measurements below 9.27(7) K indicate that a fourfold degenerate non-collinear antiferromagnetic state exists with almost complete ordering of the Mn2+ spins. Muon spin relaxation measurements provide a local probe of the magnetic fields inside this material over the t1/2 = 2.2 µs lifetime of a muon, indicating a slightly lower Néel transition temperature of 7.9(1) K. The dc susceptibility data do not show the loss of magnetization that should accompany the onset of the antiferromagnetic order; they indicate that a strongly antiferromagnetically coupled paramagnetic state [θ = −73(3) K] persists down to 4 K, at which temperature a weak transition occurs. The behavior of this material differs considerably from the closely related compositions Ba2MnMO6 (M = W, Te), which show collinear ordering arrangements and well defined antiferromagnetic transitions in the bulk susceptibility. This suggests that the Mo6+ cation leads to a fine balance between the nearest and next-nearest neighbor superexchange in these frustrated double perovskite structures.

High-pressure structural transition and magnetic phase diagram of CuB2O4

Noncentrosymmetric $\mathrm{Cu}{\mathrm{B}}_{2}{\mathrm{O}}_{4}$ is a prototypical system with interacting spin sublattices of different dimensionality, exhibiting diverse magnetic structures and magnetic phase transitions. Here we report pressure-induced structural evolution of $\mathrm{Cu}{\mathrm{B}}_{2}{\mathrm{O}}_{4}$ and its effect on the magnetic phase diagram. Powder x-ray diffraction (XRD), Raman scattering, and infrared phonon measurements have been performed under high pressure at room temperature. Although XRD shows lattice stability up to $\ensuremath{\sim}25\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, Raman and IR phonon measurements reveal structural anomaly near 3 GPa, followed by a structural phase transition at $\ensuremath{\sim}12\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. Pressure evolution of the zero-phonon lines in the low-temperature optical absorption studies helps identifying the symmetry change of the Cu sites modifying the crystal-field energy levels at the structural transition. High-pressure magnetization measurements have been performed with magnetic field applied perpendicular to the tetragonal $c$ axis. With increasing pressure the saturation magnetization of the commensurate weak ferromagnetic phase increases with systematic reduction of its turnup critical field. Pressure-induced systematic suppression of the dc susceptibility in this phase is attributed to the reduced critical field, indicating pressure-driven enhanced stability of the weak ferromagnetic phase at high pressure. Whereas, below 10 K the critical field of the incommensurate-commensurate transition increases with pressure, indicating enhanced stability of the incommensurate helical order at high pressure.

Impact of Mn-Pn intermixing on magnetic properties of an intrinsic magnetic topological insulator: the µSR perspective

We investigated the magnetic properties of polycrystalline samples of the intrinsic magnetic topological insulators MnPn2Te4, with pnictogen Pn = Sb, Bi, by bulk magnetization and µSR. DC susceptibility detects the onset of magnetic ordering at TN = 27 K and 24 K and a field dependence of the macroscopic magnetization compatible with ferri- (or ferro-) and atiferro- magnetic ordering, respectively. Weak transverse field (wTF) Muon Spin Rotation (µSR) confirms the homogeneous bulk nature of magnetic ordering at the same two distinct transition temperatures. Zero Field (ZF) µSR shows that the Sb based material displays a broader distribution of internal field at the muon, in accordance with a larger deviation from the stoichiomectric composition and a higher degree of positional disorder (Mn at the Pn(6c) site), which however does not affect significantly the sharpness of the thermodynamic transition, as detected by the muon magnetic volume fraction and the observability of a critical divergence in the longitudinal and transverse muon relaxation rates.

Pressure tuning of structure, magnetic frustration, and carrier conduction in the Kitaev spin liquid candidate Cu2IrO3

The layered honeycomb lattice iridate Cu$_2$IrO$_3$ is the closest realization of the Kitaev quantum spin liquid, primarily due to the enhanced interlayer separation and nearly ideal honeycomb lattice. We report pressure-induced structural evolution of Cu$_2$IrO$_3$ by powder x-ray diffraction (PXRD) up to $\sim$17 GPa and Raman scattering measurements up to $\sim$25 GPa. A structural phase transition (monoclinic $C2/c \: \rightarrow$ triclinic $P\bar{1}$) is observed with a broad mixed phase pressure range ($\sim$4 to 15 GPa). The triclinic phase consists of heavily distorted honeycomb lattice with Ir-Ir dimer formation and a collapsed interlayer separation. In the stability range of the low-pressure monoclinic phase, structural evolution maintains the Kitaev configuration up to 4 GPa. This is supported by the observed enhanced magnetic frustration in dc susceptibility without emergence of any magnetic ordering and an enhanced dynamic Raman susceptibility. High-pressure resistance measurements up to 25 GPa in the temperature range 1.4--300 K show resilient non-metallic $R$($T$) behaviour with significantly reduced resistivity in the high-pressure phase. The Mott 3D variable-range-hopping conduction with much reduced characteristic energy scale $T_0$ suggests that the high-pressure phase is at the boundary of localized-itinerant crossover. Using first-principles density functional theoretical (DFT) calculations, we find that at ambient pressure $\rm Cu_2IrO_3$ exists in monoclinic $P2_1/c$ phase which is energetically lower than $C2/c$ phase (both the structures are consistent with experimental XRD pattern). DFT reveals structural transition from $P2_1/c$ to $P\bar{1}$ structure at 7 GPa (involving dimerization of Ir-Ir bonds) in agreement with experimentally observed transition pressure.

Inverted magnetic response in severe plastically deformed nanostructured high-entropy alloy

We present unconventional magnetization in a high-pressure torsion (HPT) CoCrFeNi nanostructured high-entropy alloy: (i) the temperature dependent magnetization protocol and DC susceptibility suggest effects of spin-clustering. Moreover, HPT-processing of the alloy produces a heterogeneous and metastable nanostructure, changing its supermagnetic character: turning superparamagnetic to superspin glass dynamics, (ii) the material shows an inverted magnetic hysteresis loop, an inversion of the central part of the loop where the remanent magnetization points in a direction opposite to the applied field. The exquisite tunability of this inverted magnetism as a function of field and temperature and its reproducibility in a quasi-equilibrium setting make this spin-clustering phenomenon unique. We account for this phenomenon in terms of a non-equilibrium population of oppositely polarized domains of an ordered ferromagnetic state, enabled through the nanostructured, highly distorted, and locally disordered crystalline medium.

Synthesis, Supramolecular Insight, Hirshfeld Surface Analyses and Magnetic Properties of Two Lanthanide Complexes of 1,8-naphthalene Dicarboxylate

Two isostructural mononuclear complexes of Lanthanides (Ln = La and Pr) constructed from 1,8-naphthalene dicarboxylate (NDC) and 1,10-Phenanthroline (Phen) as auxiliary ligand are reported. Both the complexes were formed through an in situ hydrolytic ring opening reaction of 1,8-naphthalic anhydride with Phen ligands. 3D supramolecular structures are observed which are guided by different weak interactions. The crystal structures of both the complexes were determined by single crystal X-ray diffraction. The room temperature photoluminescence studies, carried out in the powder state displayed three noticeable peaks from excited ( 3 P J ; J = 2, 1, and 0) to ground state ( 3 H 4) at ~464, 497, and 538 nm respectively, under UV excitation. Temperature dependent dc susceptibility (c = M/H) as a function of temperature is investigated where Pr-complex shows antiferromagnetic behavior. The Hirshfeld surface analysis of the two complexes is also described.

Probing the Magnetization Relaxation Dynamics of Four-Coordinate Lanthanide(III) Complexes

The reaction of bulky trimethylsilylanilide (N-TMSA) ligand with various lanthanide salts led us to isolate unusual and unique four-coordinate monomeric Ln(III) complexes which are challenging to isolate and not surprisingly rare in the literature. The single crystal X-ray diffraction unveils that all the complexes are monomeric and isostructural with the general molecular formula of [Ln(N-TMSA)3(THF)] where Ln = Dy (1) or Yb (2). Both complexes are found to possess distorted tetrahedral geometry. For all the complexes, detailed dc and ac susceptibility measurements were performed and both 1 and 2 show frequency-dependent out-of-phase susceptibility signals only in the presence of an optimum external magnetic field. The experimental observations are well supported by theoretical calculations and developed magneto-structural correlation using the various model complexes.

Nickel substitution induced reentrant spin glass behavior in EuGa4

Typically, atomic scale disorder is essential to show glassy behavior and amorphous materials can be the optimum candidates in this regard. Generating local disorder in an ordered material by substitution of another metal is a challenging task. In this paper, we successfully substituted Ni in ${\mathrm{EuGa}}_{4}$ (${\mathrm{EuNi}}_{0.37}{\mathrm{Ga}}_{3.63}$) to induce spin glass (SG) behavior. The compound was characterized by single-crystal x-ray diffraction, dc magnetization, frequency-dependent ac susceptibility, isothermal magnetization at various temperatures, spin relaxation, specific heat, and electric resistivity. Two distinct anomalies were observed in dc susceptibility $\ensuremath{\sim}16.5$ and 5.2 K corresponding to long-range antiferromagnetic (AFM) ordering and SG transition, respectively. Their characteristic peaks in specific heat capacity further support the AFM and SG behavior. The irreversibility temperature is fitted with the Almeida-Thouless equation, confirming the Ising SG. The SG behavior is further confirmed by shift of maxima to a high temperature in ac susceptibility with increasing frequency. Nonzero spin relaxation after 7200 s, fitted with stretched exponential model, provides the value of $\ensuremath{\beta}=0.41$. This material can be identified as a possible reentrant SG as AFM and SG behavior coexist in the low-temperature range. Additionally, a spin-flip transition is observed in the AFM region ($5.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}&lt;T&lt;16.5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$). Our first-principles calculations show Ni substitution induces the distortion in electronic band structure as compared with parent ${\mathrm{EuGa}}_{4}$. A minimal difference between the different magnetic configurations for Ni-substituted ${\mathrm{EuGa}}_{4}$ suggests the frustration in the lattice, pointing toward SG behavior.

Evidence for cluster glass ground state in the potential giant dielectric constant material Ba(Fe1/2Sn1/2)O3-δ

We report the magnetic ground state of the technologically important giant dielectric constant material Ba(Fe1/2Sn1/2)O3-δ (BFSO) using detailed dc and ac magnetization and specific heat measurements. Our careful x-ray diffraction analysis confirms that BFSO is single phase and crystallizes in the cubic structure with the Pm3¯m space group. Temperature-dependent dc susceptibility measurements reveal that magnetic irreversibility sets in below Tirr ~ 18 K. In addition, the zero-field cooled susceptibility exhibits a peak at the freezing temperature Tf ~ 16 K, which is also characterized by a frequency dispersion in ac susceptibility measurements. This data also confirms to the critical slowing down model with cluster-glass transition temperature TG ~15.7 K and characteristic relaxation time τo ~10−7 s. The magnetic field dependence of the freezing temperature Tf obeys de Almeida-Thouless line in the H-T plane. The presence of aging effect and extremely slow time decay of thermoremanent magnetization is also observed below Tf. The magnetic contribution to the specific heat (Cm) exhibits a linear temperature dependence below Tf. All these observations unambiguously confirm a cluster-glass magnetic ground state in this system.

Possible realization of three-dimensional quantum spin liquid behavior in HoVO4

The study of geometrically frustrated magnetic systems with unusual crystal field ground states offers a possibility of realizing the new aspects of physics of disordered systems. In this study, we report our results of structural, magnetic susceptibility, heat capacity measurements, along with density functional theory (DFT) calculations on HoVO4; a compound in which the presence of a distorted kind of HoO8 polyhedral leads to multiple magnetic interaction paths. The observed broad maximum below 10 K in the temperature response of DC susceptibility curves implies the presence of short-range correlations. AC susceptibility rules out the possibility of any kind of spin freezing. Temperature dependent heat capacity measurement at zero field indicate towards the absence of long-range ordering, along with the presence of a broad maximum centered around 14 K. The residual heat capacity exhibits a characteristic power-law (Tα ) behavior with the exponent α nearly equal to 2, which is analogous to that observed for other three-dimensional (3D) quantum spin liquid (QSL) systems. The DFT calculations signify the presence of dominant second and third nearest neighbor interactions, which in turn lead to magnetic frustration in our system. Our investigations suggest that HoVO4 can be a candidate for realizing a 3D QSL state.

Anisotropic spin-glass and magnetic behavior in single-crystalline U2PtSi3

The results of ac and dc susceptibilities, magnetization, magnetic relaxation, electrical resistivity, and specific heat measurements performed on a hexagonal AlB2-type single-crystalline U2PtSi3 are reported. The previously reported spin-glass transition in polycrystalline U2PtSi3 was confirmed to also occur in the single-crystalline sample with spin freezing temperature Tf=12.4 K. It is newly found that the spin-glass effect and magnetic behavior of U2PtSi3 measured along and perpendicular to the hexagonal c-axis show different magnetic field responses. Along the hard magnetization axis (c-axis), both the rate of change of Tf with the magnetic field and the detected magnetic viscosity coefficient are much smaller than those obtained in the c-plane. On the other hand, the low-temperature specific heat measurement yields an enhanced coefficient of the linear temperature term, and the temperature dependence of electrical resistivity illustrates a shallow minimum at the temperature much larger than Tf. The possible mechanisms for these phenomena are discussed by comparing with the corresponding properties observed in other ternary 2:1:3 uranium intermetallic compounds.