Prof. Subhash Thota
Department of Physics, Indian Institute of Technology Guwahati, India
Date & Time: 14:30 - 15:30, December 5th (Fri), 2025.
Place: Room#513-514, Advanced Structural Materials Bldg. 5F, Sengen.
Exploring the Field-Induced Magnetic Transitions to Study Quantum Critical Excitations in Spin-1 and 1/2 Antiferromagnets
Prof. Subhash Thota
Department of Physics, Indian Institute of Technology Guwahati, India
Abstract:
Recent years have witnessed growing interest in the study of strongly correlated phenomena within the Columbite family of compounds, driven by their intriguing magnetic and electronic properties [1]. These materials provide an ideal platform for exploring quantum magnets and for testing the predictions of theoretically solvable models. Columbites are typically complex transition-metal oxides with the general formula AB2O6, where the A and B sites are occupied by transition-metal cations in divalent and pentavalent oxidation states, respectively. They crystallize in an orthorhombic structure with space group Pbcn (D142h) [1,2]. These systems are particularly fascinating because they exhibit a variety of unconventional phenomena, including quantum critical behavior, magnetoelectric coupling, Tricritical behavior (Fig. 1), and field-induced metamagnetic transitions. Although real magnetic systems are inherently three-dimensional, the magnetic interactions in Columbites can often be approximated as quasi-one-dimensional (quasi-1D) or quasi-two-dimensional (quasi-2D) depending on the dominant spin-chain coupling directions. This reduction in magnetic dimensionality gives rise to quantum phenomena such as quantum phase transitions near the quantum critical point (QCP) under a transverse magnetic field, thereby realizing the Transverse-Field Ising Chain (TFIC) model in real materials. In this talk, I will present some of these unique features and discuss the nature of exchange interactions in selected S = 1/2 and S = 1 Columbite systems, highlighting their relevance to the broader field of quantum magnetism.
References:
[1] S. Thota et.al., Phys. Rev. B 103, 064415 (2021).
[2] R. Maruthi et.al., Phys. Rev. B 108, 224430 (2023).
References:
[1] S. Thota et.al., Phys. Rev. B 103, 064415 (2021).
[2] R. Maruthi et.al., Phys. Rev. B 108, 224430 (2023).
Figure 1 : H-T phase diagram of NiNb2O
6 sample for H parallel to the a axis in (a) and H parallel to the c axis yielding a triple point, TTP (π»,π) = (5 kOe, 5.50 K) in (b). Lines connecting the data points are visual guides, and references to sources of the data points are listed in the figure. The acronyms used for the magnetic phases are as follows: PM, paramagnetic; AFM, antiferromagnetic; and IFM, induced ferromagnetic.
(Contact)
Hiroaki Sukegawa, Group Leader, Spintronics Group, Research Center for Magnetic and Spintronic Materials (CMSM)
E-mail: SUKEGAWA.Hiroaki[at]nims.go.jp
E-mail: SUKEGAWA.Hiroaki[at]nims.go.jp