Here, we investigate the structural, magnetic, and dielectric properties in thin films of double-perovskite Sr2NiMoO6, which consists of an alternate arrangement of magnetic Ni2+ (spin-1) and nonmagnetic Mo6+ ions with tetragonal-I4/m lattice symmetry. The bulk Sr2NiMoO6 is an antiferromagnet (AFM) with a Neel temperature TN similar to 80 K. Thin films are grown with three different thicknesses (25, 40 and 60 nm) on SrTiO3 (100) substrates using pulse laser deposition technique. The magnetization measurements on films reveal that an AFM interaction is retained, however, the ordering temperature TN reduces in the range (41-55) K, depending on the film thickness. This change in magnetic behavior is attributed to the lattice strain induced by the interaction between the thin film and the substrate. Temperature and frequency dependent dielectric properties have been investigated in selected SNMO film (similar to 40 nm), integrating inside metal electrodes. A Maxwell-Wagner type relaxation is found over whole frequency range down to low temperature in present film. Our Cole-Cole plot analysis suggests a dominant contribution of grain-boundary to dielectric behavior compared to grains, which increases with lowering temperature.

Here, we report an interesting magnetic oxide NaNiSbO, where the interplay between exchange interactions and lattice symmetry crucially influence its exotic ground state (GS). This compound features a layered honeycomb lattice with magnetic Ni(spin-1) surrounding nonmagnetic Sbcenters. The x-ray absorption and magnetic circular dichroism measurements confirm a Nicharge state with notable spin and orbital moments at room temperature. The material exhibits antiferromagnetic (AFM) ordering around 17 K () and a field-induced magnetic transition at lower temperatures. Our measurements reveal a low-temperature anomaly, likely linked to glassy behavior. The power-law magnetic specific heat suggests mixed magnon dispersion, while low magnetic entropy indicates a highly degenerate GS. Neutron diffraction data point to a zigzag-type AFM GS, with a reduced site moment of 1.34(3)at 2.5 K that disappears near 17.2 K, consistent with bulk data. Lattice parameters show anomalies atand lower temperatures. Ab-initio calculations support zigzag spin order and imply a competing in-plane Niinteractions that causes spin frustration. Overall, our combined experimental and theoretical study uncovers the microscopic magnetic GS of NaNiSbOas a mix of long-range zigzag AFM and a glassy state, advancing the understanding of frustrated honeycomb magnets.

Abstract The complex interplay between spin–orbit coupling, magnetism, and magnetic field at the interface of a heterostructure, consisting of ferromagnet (FM) and heavy metal (HM), often exhibits extraordinary magnetic and electric phenomena, where an in-plane Dzyaloshinskii–Moriya (DM) interaction plays a crucial role in stabilizing local spin texture in the FM layer. Here, we report detailed magnetic and magneto-transport behavior on an epitaxially grown thin heterostructure with 3d FM La0.67Ca0.33MnO3 (LCMO) and 5d HM SrIrO3 (SIO). Magnetic measurements show an unusual development of magnetic ordering in SrIrO3 around 42 K, which further leads to a Mn/Ir magnetic coupling at the interface. The magnetoresistance (MR) measurements show an evolution of its value and shape with the magnetic state of this bilayer. While MR is negative at high temperatures, it shows a positive-to-negative crossover with stable magnetic ordering of LCMO, and finally, the positive MR exhibits an asymmetry at low temperatures with the ordering of SIO. While we ascribe this unusual MR behavior to interface-driven varying spin scattering between itinerant and localized electrons, our results shed light on comprehending the complex but tunable interface behavior on charge transport in a particularly designed heterostructure, offering valuable insights for future functional material engineering.

Valence fluctuations arising from quantum phenomena in the magnetic kagome lattice offer a unique platform to study the instabilities in charge configuration associated with magnetic interactions. Here, we report the evidence of valence fluctuation in Fe1−yCoySn from x-ray absorption and resonant photoemission measurements. Both the magnetization and magnetoresistance measurements showed an interplay of ferromagnetic and antiferromagnetic interactions, which have temperature and field dependence. An increase in the doping concentration y increases the ferromagnetic interaction in the kagome layer, while the antiferromagnetic interaction in the adjacent kagome layer decreases. We find that the Fe2+ and Co2+ states are associated with ferromagnetic interactions and have localized characters near the Fermi level (EF), while Fe3+ and Co3+ have antiferromagnetic contributions with delocalized characters and lie far away from the EF. A systematic decrease in the density of Fe3+ and Co3+ states over the density of Fe2+ and Co2+ states is observed with increasing y. Thus, the magnetic ordering in Fe1−yCoySn depends on the magnitude of the 2+ and 3+ states of Fe and Co at and near the EF, while the change in spin orientation with an increase in y depends on the changes in spin–orbit coupling and the hybridization between the Fe and Co valence electrons. Hence, Fe1−yCoySn is found to be a valence fluctuating material where the spin state of electrons can be controlled by doping, temperature, and magnetic field, which promises important applications of this material in spintronic, magnetic sensor, and high density data storage devices.

Antiferromagnetic Kagome semimetal FeSn has gained significant attention due to the presence of topological flat bands and Dirac fermions. There has been immense interest to tune the bands with doping in FeSn for enhancing the magnetic and transport properties. Here, we report an experimental study of transport, magnetization, and electronic structure of Fe1-yCoySn as a function of Co-doping concentration (y). Variation in the temperature-dependent resistivity with increasing y is associated with the increase in spin-dependent scattering. Co doping in FeSn gives rise to canted antiferromagnetism with the decrease in the Neel transition temperature (T-N). The local moment of Co and Fe atoms has been estimated from the analysis of 3s core levels. The decrease in T-N with increasing y is due to the decrease in the local moment of Fe atoms. The systematic shift in the valence states away from the Fermi level (E-F), and the valence band broadening with the increase in y indicate an increase in the electron correlation and hybridization effects in Fe1-yCoySn. An increase in both electron correlation and hybridization with doping leads to the strong magnetic interaction between the local moments of Fe and Co atoms which gives rise to the canted antiferromagnetism in Fe1-yCoySn.

We report the magnetic response of the multiferroic compound YMn2O5 up to 16 T magnetic field. YMn2O5 undergoes a paramagnetic to incommensurate magnetic phase transition below T similar to 45 K and progressively followed by commensurate and incommensurate magnetic phases at further lower temperatures. The commensurate to incommensurate phase transition at low temperatures shows a broad thermal hysteresis in the magnetization (M(T)) measurements performed in the cooling and heating cycles. This suggests a first-order transition and phase-coexistence across a wide temperature and field regime. Most interestingly, M exhibits signatures of metastable glassy state at low temperatures and high magnetic fields. We show that the high-temperature phase persists down to the lowest temperature when cooled at high fields. This indicates that the first-order transition between the two magnetic phases is kinetically arrested at high fields. As a result, the true magnetic state of YMn2O5 is obscured and it gives rise to the phase co-existence and thermodynamically non-equilibrium magnetic state.

Antiferromagnetic Kagome semimetal FeSn has gained significant attention due to the presence of topological flat bands and Dirac fermions. There has been immense interest to tune the bands with doping in FeSn for enhancing the magnetic and transport properties. Here, we report an experimental study of transport, magnetization, and electronic structure of Fe _1-y Co _y Sn as a function of Co-doping concentration (y). Variation in the temperature-dependent resistivity with increasing y is associated with the increase in spin-dependent scattering. Co doping in FeSn gives rise to canted antiferromagnetism with the decrease in the Neel transition temperature ( T_N ). The local moment of Co and Fe atoms has been estimated from the analysis of 3s core levels. The decrease in T_N with increasing y is due to the decrease in the local moment of Fe atoms. The systematic shift in the valence states away from the Fermi level ( E_F ), and the valence band broadening with the increase in y indicate an increase in the electron correlation and hybridization effects in Fe _1-y Co _y Sn. An increase in both electron correlation and hybridization with doping leads to the strong magnetic interaction between the local moments of Fe and Co atoms which gives rise to the canted antiferromagnetism in Fe _1-y Co _y Sn.

The path dependence of the magnetocaloric effect (MCE) in CoS _1.76 Se _0.24 has been studied. A field-induced paramagnetic (PM)-ferromagnetic (FM) transition results in 4.6 J/kg-K peak value of isothermal entropy change ( Δ S _th ) for 90 kOe field change. Above 10 K, the temperature dependence of Δ S _th calculated from the forward curve (0 kOe–90 kOe) and that calculated from the reverse curve (90 kOe–0 kOe) are found to be similar, whereas at lower temperature, contrasting behaviour is observed due to the kinetic arrest of first-order magnetic transition.

A comparative specific heat (C _P ) study of GdPdAl and TbPdAl compounds crystallizing in hexagonal ZrNiAl-type crystal-structure (space group P 6̅ 2 m) is presented. Consistent with earlier reports both the compounds show the signature of two magnetic transitions in magnetization data. The magnitude of the jump in C _P at the high-temperature transition at T _N1 ( ∼ 47 K ) in GdPdAl indicates ordering into an amplitude-modulated magnetic structure. The analysis of magnetic entropy change (S _4f ) showed that about one-half of total S _4f occurs below low temperature transition at T _N2 . This is in contrast to that seen in TbPdAl, where only one-third of the entropy of transition occurs below T _N2 . For both the compounds S _4f tends to saturate to about 84 _N1 ) of that expected for complete ordering of the rare earth moments, indicating incomplete removal of geometrical frustration.

Band engineering in magnetic kagome material has gained interest due to the emergence of novel quantum magnetism that arises from the interplay between topology and electron correlations. Here, we report a detailed study on the crystal structure, magnetization, and electronic structure of Fe1-yCoySn as a function of composition (y). The kagome lattice of Fe1-yCoySn is found to shrink with the increase in y. A decrease in the antiferromagnetic transition temperature (T-N) and changes in spin orientation is observed in the magnetization for y > 0. Core-level analysis showed a systematic decrease in the local moment of Fe and an increase in the local moment of Co with increasing y. Valence-band broadening and shifting of the bands away from the Fermi level (E-F) in Co-doped compositions are associated with enhanced hybridization and the correlation effects that give rise to localized and quasilocalized states near E-F. The band structure of FeSn (001) and Fe0.95Co0.05Sn (001) surfaces along the K- Gamma-M direction showed evidence of quasilocalized and localized flat bands. We find that there is an interplay between the Coulomb correlation and hybridization in Co-doped composition that gives rise to the broadening of the flat band and a shift of the Dirac point away from E-F and in k-space. The decrease in T-N with increasing y is associated with the correlation effects, which broaden the flat band and shift the Dirac point away from E-F, while the shift of the Dirac point in k-space is a signature of change in the magnetocrystalline anisotropy due to spin orientation.

beta-V1-xTix alloy superconductors are considered to be promising materials for high magnetic field applications. So far, attempts to improve the critical current density (JC) of beta-V1-xTix alloys have shown limited success. Improving JC requires a controlled generation of defects. Similar to the V0.6Ti0.4-RE (RE = Gd, Y) alloys, RE = Ce, Dy and Nd are also immiscible in the V0.6Ti0.4 matrix. The superconducting transition temperature (TC), upper critical field (HC2), irreversibility field (HIrr), and JC increase with the RE addition. However, the tensile strength of V0.6Ti0.4-Gd alloy is observed to be significantly lower than that of V0.6Ti0.4 alloy. Cold-working is found to further improve the TC, HC2, HIrr, and JC of all the V0.6Ti0.4-RE alloys. Successive cold-working (with 50% reduction of thickness each time) and annealing (SCA) at 450 circle C for 5 hrs is found to significantly improve the HIrr, and JC of V0.6Ti0.4-RE (RE = Gd, Ce) alloys. The tensile strength is also found to increase to about 60-70% of the V0.6Ti0.4 alloy after the third annealing. It is observed that alpha ' and omega phases form at the defect sites at various stages of cold-working and annealing. JC(H = 0) and HIrr are about 840 Amm-2 and 7 T respectively for the ascast V0.6Ti0.4-RE alloys. Cold-working on the V0.6Ti0.4-RE alloys further improves the JC(H = 0) and HIrr to about 1250 Amm- 2 and 8.45 T respectively. SCA increases the JC(H = 0) and HIrr to about 4000 Amm- 2 (or more) and 9 T respectively, and the JC(7 T) to about 500 Amm- 2 in V0.6Ti0.4-RE alloy at 4 K. We present a detailed description of the defect structure in these alloys and its role in pinning the magnetic flux lines, thereby improving the overall JC.

FeRh 0.8 Pd 0.2 is known to exhibit near room-temperature first-order antiferromagnetic (AF)–ferromagnetic (FM) transition, typical of chemically ordered FeRh system. In addition, it is also reported to show martensitic transition at a lower temperature. In this work, the effect of sample history on transition temperature (Tt) and the magnetocaloric effect (MCE) have been studied. The experimentally determined MCE parameters across FM to AF transition induced either by isothermal magnetic field sweep or by temperature sweep showed a large isothermal change in entropy around room temperature, i.e., 14 J/kg K for 50 kOe magnetic field change, whereas MCE corresponding to AF–FM transition depends on cooling history. Our study shows that in the presence of martensite phase, the peak value of MCE is shifted to higher temperatures but with significantly reduced magnitude.

The idea of strain based manipulation of spins in magnetic two-dimensional (2D) van der Waal (vdW) materials leads to the development of new generation spintronic devices. Magneto-strain arises in these materials due to the thermal fluctuations and magnetic interactions which influences both the lattice dynamics and the electronic bands. Here, we report the mechanism of magneto-strain effects in a vdW material CrGeTe _3 across the ferromagnetic (FM) transition. We find an isostructural transition in CrGeTe _3 across the FM ordering with first order type lattice modulation. Larger in-plane lattice contraction than out-of-plane give rise to magnetocrystalline anisotropy. The signature of magneto-strain effects in the electronic structure are shift of the bands away from the Fermi level, band broadening and the twinned bands in the FM phase. We find that the in-plane lattice contraction increases the on-site Coulomb correlation ( U_eff ) between Cr atoms resulting in the band shift. Out-of-plane lattice contraction enhances the d-p hybridization between Cr–Ge and Cr–Te atoms which lead to band broadening and strong spin-orbit coupling (SOC) in FM phase. The interplay between U_eff and SOC out-of-plane gives rise to the twinned bands associated with the interlayer interactions while the in-plane interactions gives rise to the 2D spin polarized states in the FM phase.

Strong spin-lattice coupling makes external pressure (P) an important parameter across a first-order magnetostructural phase transition. Here, we have studied the effect of P under different magnetic fields on the phase coexistence and kinetics of nucleation and growth around such transitions in two prototype systems Pr0.5Ca0.5Mn0.975Al0.025O3 and La0.5Ca0.5MnO3, where the ferromagnetic-metal and antiferromagnetic-insulator phases compete in real space. We have determined the H - P phase diagram of supercooling and superheating temperatures. The change in supercooling and superheating temperatures and the nucleation and growth control the phase coexistence. Surprisingly, despite having contrasting ground states, in both Pr0.5Ca0.5Mn0.975Al0.025O3 and La0.5Ca0.5MnO3 the transformation rate between the two states is suppressed at higher pressure. This proves that there must be some universal phenomena controlling the dynamics. Different spin and structural order at the interface of the two phases appear to be responsible for giving rise to strong frustration and eventually hindering the kinetics, resulting in the stabilization of glasslike behavior.

Here, we report detailed lattice structure, magnetization (dc and ac) and specific heat measurements on a 3d-5d based new triple-perovskite material Sr3CuIr2O9. The Sr/Cu forms a layered structure of triangular-lattice while the Ir forms Ir2O9 dimers which lie in chain as well as simultaneously makes layered triangular-lattice with neighboring atoms. Due to random site-sharing with Sr2+, the Cu2+ (3d(9), spin-1/2) forms a diluted magnetic lattice, thus giving a disordered in-plane exchange interaction. Opposed to conventional Jeff model, the Ir5+ (5d(4), J(eff) = 0) is believed to be magnetic here which participates both in-chain and in-plane magnetic interactions. This complex lattice structure driven competing exchange interaction leads the ground state to a gapless quantum-spin-liquid state which coexists with (weak) ferromagnetic spin correlations. While underling the importance of spin state (spin-1/2), we believe that the combined effect of lattice structure, geometric frustration, spin-orbit coupling and spin state has given rise this interesting ground state in this material.

The idea of strain based manipulation of spins in magnetic two-dimensional (2D) van der Waal (vdW) materials leads to the development of new generation spintronic devices. Magneto-strain arises in these materials due to the thermal fluctuations and magnetic interactions which influences both the lattice dynamics and the electronic bands. Here, we report the mechanism of magneto-strain effects in a vdW material CrGeTe[Formula: see text] across the ferromagnetic (FM) transition. We find an isostructural transition in CrGeTe[Formula: see text] across the FM ordering with first order type lattice modulation. Larger in-plane lattice contraction than out-of-plane give rise to magnetocrystalline anisotropy. The signature of magneto-strain effects in the electronic structure are shift of the bands away from the Fermi level, band broadening and the twinned bands in the FM phase. We find that the in-plane lattice contraction increases the on-site Coulomb correlation ([Formula: see text]) between Cr atoms resulting in the band shift. Out-of-plane lattice contraction enhances the [Formula: see text] hybridization between Cr-Ge and Cr-Te atoms which lead to band broadening and strong spin-orbit coupling (SOC) in FM phase. The interplay between [Formula: see text] and SOC out-of-plane gives rise to the twinned bands associated with the interlayer interactions while the in-plane interactions gives rise to the 2D spin polarized states in the FM phase.

Here we report the evidence of an additional magnetic ordering and frequency dispersive magneto-dielectric (MD) permittivity besides multiferroic behavior in Te4+(S= 0) doped FeVO4. Two antiferromagnetic transitions similar to FeVO4at ∼21.86 K (TN1) and 16.03 K (TN2) were observed in all samples. An additional novel defect clusters based magnetic ordering at relatively higher temperature (TAMO) ∼ 203 K is also observed from the magnetization. Evaluated magnetic moments show systematic decrease and the magnetic frustration factors show an increase with the increasing of Te4+(S= 0) content. MD studies show stable ferroelectric ordering at spiral magnetic transition (TN2) and the multiferroic order persists to the largest doping of Te (x= 0.10). The MD studies also reveal a magneto-capacitive (MC) behavior at TAMO(∼203 K) with a high dielectric constant and loss, and the possible reason for the magnetic ordering and MC behavior is ascribed to short range magnetic clustering arising out of defect based mechanisms. Mössbauer spectroscopic studies confirm local structural correlation with magnetic and ferroelectric ordering.

The magnetic susceptibility of elemental copper (Cu) shows an anomalous rise at low temperatures superimposed on the expected atypical diamagnetic response. Such temperature-dependent susceptibility, which is also known as the Curie tail, cannot be explained on the basis of the Larmor diamagnetic and Pauli paramagnetic contributions expected in Cu. Using valence band resonant photoemission spectroscopy results and density functional theory calculations, we show the magnetic anomaly appears due to the presence of holes in the Cu 3d band, which originates from a thermally excited electronic configuration. Our study therefore highlights that the Curie tail, which is generally overlooked presuming it is either due to paramagnetic impurities or defects, can in fact be intrinsic to a material, and even simple systems such as elemental Cu are susceptible to electronic excitations giving rise to an anomalous magnetic state.