Research Highlights

Existence of complex magnetic ground state and topological Hall effect in centrosymmetric silicide DyScSi

Topological Hall effect driven by a complex magnetic ground state is realized in a centrosymmetric system, DyScSi. Temperature dependent magnetization and neutron diffraction results establish the presence of commensurate antiferromagnetic phase around 92 K, followed by an incommensurate antiferromagnetic phase below 40 K. Two cluster glass transitions near 20 and 8 K, are also noted. These observed features arise due competing antiferromagnetic and ferromagnetic interactions. Additionally, a finite contribution of topological Hall effect is observed in the intermediate field regime (8–30 kOe), at low temperature.


K. Yadav  et  al,  New J. Phys. 25, 123030(2023) 

Nonequilibrium dynamics and discretization of energy levels in the inverse spinel LiCoVO4 

Realization of persistent discrete energy states in Co-based compounds due to unquenched orbital angular momentum remains an exciting perspective in systems which favour mixed state of Co2+ and Co3+ ions, without any chemical substitution. Structural investigations reveal the presence of anti-site disorder between V and Co results in Co3+ ions along with the expected Co2+ ions. A thorough investigation of AC susceptibility reveal the presence of cluster glass state below 3 K, strengthened by relaxation and memory effect measurements. The detailed analysis of the observed Schottky anomaly reveal the presence of persistent discrete energy state of Co3+ ions which appears due to octahedral distortion and spin-orbit coupling.

 

Dheeraj Ranaut  et  al,  Phys. Rev. B 107, 214413 (2023)

Anti-site disorder driven short-range order and canted antiferromagnetism in LiNiVO4 

Structural investigations reveal that unlike usual cation ordering, Ni and Li ions are randomly distributed at octahedral sites and results in reduced magnetic frustration. Further, an additional anti-site disorder is present, as a small fraction of Ni ions occupies tetrahedral sites. Magnetic susceptibility and heat capacity studies show that short-range magnetic corelations develop below 30 K, followed by a canted antiferromagnetism below 2.2 K. Different competing magnetic interactions due to the presence of disorder and reduced magnetic frustration result in the short-range ordering as well as canted antiferromagnetism in LiNiVO4.  

Dheeraj Ranaut  et  al,  J. Magn. Magn. Mater 578, 170833 (2023)

Multiband superconductivity in non-centrosymmetric full Heusler LuPd2Sn

Our studies reveal that LuPd2Sn is a type II superconductor and undergoes superconducting transition below 2.5 K. Above 2.5 K, the temperature and field dependence of resistivity indicate to the presence of multiple bands and inter-band phonon assisted scattering. The upper critical field, HC2 exhibits linear behaviour and deviates from Werthamer, Helfand and Hohenberg model over the measured temperature range. Additionally, the Kadowaki–Woods ratio plot supports the unconventional superconductivity in this alloy. Moreover, a significant deviation from the s-wave behaviour is noted, which is studied using phases fluctuation analysis. It indicates the presence of spin triplet along with spin singlet component arising due to antisymmetric spin orbit coupling.  

Kavita Yadav  et  al,  J. Phys. Condens. Matter 35, 275601 (2023)

Low dimensional magnetism in PrVO4

Signatures of low dimensional (D) magnetic ground state are established in a rare-earth orthovanadate PrVO4 (S=1). The fourth near neighbor Pr atoms form uniform chains, separated via the non-magnetic VO4 tetrahedra - an important condition for low D magnetism. DC susceptibility and magnetic heat capacity exhibit a broad maximum implying the presence of low D magnetic ground state. The near zero value of magnetic heat capacity signifies the presence of spin gap in the excitation spectra.  

Dheeraj Ranaut et al, Phys. Chem. Chem. Phys. 25, 4305 (2023)

 Possible quantum spin liquid state in HoVO4

Novel quantum spin liquid (QSL) state is realised in HoVO4 via the means of experimental as well as computational techniques. Short-range correlations develop at low temperatures and the residual heat capacity follows quadratic dependence on temperature in the region of these correlations. This power law dependence matches very well with other 3D QSL materials. DFT calculation of magnetic interactions indicate towards the presence of strong magnetic frustration which results in the possible 3D QSL behavior.

Dheeraj Ranaut et al, J. Phys. Condens. Matter 34, 485803 (2022)

Melting of spin ice state and 5th order susceptibility in Tb2Sn2O7

In this work, in Tb2Sn2O7, following queries are investigated that whether with magnetic fields i) ordered spin-ice state is stable; ii) crystal field splitting energy is modified; iii) there is any phase transitions associated with higher-order moments. The splitting δ between the singlet-singlet states is enhanced in the presence of magnetic field, which may possibly destabilize the ordered spin-ice state. On increasing the magnetic field above 10 kOe, Zeeman energy related with the magnetic anisotropy starts dominating, which results in the formation of magnetic phase associated with fifth order susceptibility. 

Karan Singh  et  al,  New J. Phys. 24, 073037 (2022)

Glassy dynamics in Ru substituted CaHfO3 

The presence of cluster glass (CG) phase is observed in the insulating perovskite CaHf1-xRuxO3 (0 ≤ x ≤ 0.50), confirmed through both static and dynamic susceptibility. Further, CG phase is characterized by non-equilibrium dynamical measurements such as magnetic relaxation, aging effect and memory effects. These studies indicate that the presence of competing short range interactions among randomly arranged Ru cations in CaHfO3.

Gurpreet Kaur  et  al, J. Phys. Condens. Matter 34, 415802 (2022)

Field tuned quantum criticality in DyVO4

Magnetic field tuned quantum critical point (QCP) is achieved at 5 kOe via the means of entropic topography. A quantum tricritical point is formed at 2.4 K at which paramagnetic, antiferromagnetic (AFM) and metamagnetic region coincides. Below this temperature, the second order line of AFM transition transforms into first order line of metamagnetic transition which continue to 0 K and results in a metamagnetic quantum critical end point at 5 kOe.

Dheeraj Ranaut  et  al,  Sci. Rep. 12, 56 (2022)

Large magnetodielectric coupling near metamagnetic transition in Ba3GdRu2O9

Long-range antiferromagnetic (AFM) ordering is observed in Ba3GdRu2O9 around 14.8 K (TN) which splits in two transitions with applied magnetic field. Along with this, field-dependent magnetization at 2 K shows three metamagnetic transitions (MMT). From dielectric response, a maximum value of the magnetodielectric (MD) coupling is observed in the vicinity of metamagnetic transition (H2). In this system, Both Gd and Ru gets align at TN, whereas, above TN, short-range magnetic ordering is possibly responsible for MD coupling. This study highlights the importance of the investigation of metamagnetic transition’s effect on MD coupling.

Sonu Chhillar  et  al,  J. Phys. Condens. Matter 34, 145801 (2022)

Optical phonon mode assisted thermal conductivity in ZrIrSb

The high temperature thermo-electric properties of p-type ZrIrSb are investigated. A significant lower magnitude of resistivity and Seebeck coefficient are observed near room temperature due to the existence of anti-site disorder between Ir/Sb and vacant sites. Lattice thermal conductivity is governed by a coupling between the acoustic and low-frequency optical phonon modes, which originates due to heavier Ir/Sb atoms. This coupling leads to an enhancement in the Umklapp processes due to the optical phonon excitations near the zone boundary, resulting in a lower magnitude of thermal conductivity.

Kavita Yadav  et  al,  J. Phys. D: Appl. Phys. 54, 495303 (2021)

Non-Fermi liquid behaviour in La-substituted CeGe

A disorder driven non-Fermi liquid (NFL) behaviour is observed in Ce0.24La0.76Ge. In this work following queries are investigated: (1) whether the NFL state is associated with the local moment fluctuations (2) whether the observed new phase is due to the presence of biquadratic exchange coupling and (3) If yes, is the biquadratic exchange coupling related to fluctuations. Theoretical and computational study using DFT+DMFT indicate that at zero field, the presence of NFL state is associated with local moment fluctuations. The scaling of non-linear dc susceptibility suggests that the field induced phase originates due to establishment of partial order parameter associated with biquadratic exchange coupling.

Karan Singh et  al,  Phys. Rev. B 102, 235137 (2020)

Effect of (Cu/Fe)O5 bipyramid size on magnetic and dielectric properties of LnBaCuFeO5 (Ln =La and Lu)

In this work, layered perovskites materials LnBaCuFeO5 (Ln = La and Lu) is investigated. La-analogue shows magnetic cluster glass behaviour at low temperature, along with glassy electric-dipole dynamics, indicating the presence of the multiclass behaviour. In contrast, for LuBaCuFeO5, AFM transition persists along with the presence of strong bifurcation at low temperature because of strong spin anisotropy. The interactions between the electric dipoles in this compound are significantly weaker, which results in the absence of glassy dipolar behaviour.

Surender Lal et  al,  J. Appl. Phys. 126, 144101 (2019) 

Superspin glass state in Er5Pd2

Even after the absence of geometrical frustration and crystallographic disorder, Er5Pd2 undergoes a spin glass like transition below 17.2 K. Analysis of AC susceptibility data indicate that the dynamics in the system are due to the presence of strongly interacting superspins rather than individual spins. Non-linear dc susceptibility analysis suggests that the glassy behavior is introduced by random dipolar interaction among the group of spins.

Mohit K. Sharma et al, J. Phys.: Condens. Matter 30, 215803 (2018)