Below you will find web links to the Google Scholar pages of some of the members of our team.
Links to view publications featuring our team members:
Additionally, you will find the abstracts of a few selected papers our team has worked on, showcasing some of the discoveries we have been involved in as well as the range of topics we work within. These publications reflect our dedication to advancing knowledge in the field of strongly-correlated materials and condensed matter physics more generally.
We report measurements on Ti4MnBi2, where a crystal structure involving linear chains of Mn ions suggests one-dimensional magnetic character. The electrical resistivity is metallic, consistent with the results of electronic- structure calculations that find a robust Fermi surface albeit with moderate electronic correlations. A Curie-Weiss fit to the magnetic susceptibility suggests that the Mn moments are in the low-spin S = 1/2 configuration. Neutron diffraction measurements detect weak antiferromagnetic order within the Mn chains, with further evidence for the small staggered moment coming from the entropy associated with the ordering peak in the specific heat as well as from the results of spin-polarized electronic-structure calculations. The antiferromagnetic moments are apparently associated with the dx2-y2 and dxy orbitals of Mn while the remaining Mn orbitals are delocalized and nonmagnetic. Strong quantum fluctuations, possibly related to an electronic instability that forms the Mn moment or to the one-dimensional character of Ti4MnBi2, nearly overcome magnetic order.
Abhishek Pandey, Ping Miao, M. Klemm, H. He, H. Wang, X. Qian, J. W. Lynn, and M. C. Aronson,
Phys. Rev. B 102, 014406 (2020).
We report the growth of high-quality single crystals of ThCr2Si2-type tetragonal BaMn2P2 and investigation of its structural, electrical transport, thermal, and magnetic properties. Our results of basal plane electrical resistivity and heat capacity measurements show that the compound has an insulating ground state with a small band gap. Anisotropic susceptibility χab, c (T ) data infer a collinear local-moment Néel-type antiferromagnetic (AFM) ground state below the ordering temperature TN = 795(15) K, which is highest among all the ThCr2Si2- and CaAl2Si2-type 122-pnictide compounds reported so far suggesting that the strength of magnetic exchange interactions is strongest in this material. The magnetic transition temperatures of BaMn2Pn2 (Pn = P, As, Sb, Bi) compounds exhibit a monotonic decrease with the increase of tetragonal unit cell parameters a and c, suggesting a strong dependence of the strength of the decisive magnetic exchange interactions on the separation between the localized spins residing on the Mn ions. The observed monotonic increase of both χab and χc for T >TN suggests that short-range dynamic quasi-two-dimensional AFM correlations persist above the TN up to the highest temperature of the measurements. The large TN of BaMn2P2 demands for systematic hole-doping studies on this material as similar investigations on related BaMn2As2 with TN = 618 K have led to the discovery of an outstanding ground state where AFM of localized Mn spins and itinerant half-metallic ferromagnetism with TC ≈ 100 K originating from the doped holes coexist together.
B. S. Jacobs and Abhishek Pandey,
Phys. Rev. Materials 7, 044410 (2023).
Magnetization, nuclear magnetic resonance, high-resolution x-ray diffraction, and magnetic field- dependent neutron diffraction measurements reveal a novel magnetic ground state of Ba0.60K0.40Mn2As2 in which itinerant ferromagnetism (FM) below a Curie temperature TC ≈ 100 K arising from the doped conduction holes coexists with collinear antiferromagnetism (AFM) of the Mn local moments that order below a Néel temperature TN = 480 K. The FM ordered moments are aligned in the tetragonal ab plane and are orthogonal to the AFM ordered Mn moments that are aligned along the c axis. The magnitude and nature of the low-T FM ordered moment correspond to complete polarization of the doped-hole spins (half-metallic itinerant FM) as deduced from magnetization and ab-plane electrical resistivity measurements.
Abhishek Pandey, B. G. Ueland, S. Yeninas, A. Kreyssig, A. Sapkota, Yang Zhao, J. S. Helton, J. W. Lynn, R. J. McQueeney, Y. Furukawa, A. I. Goldman, and D. C. Johnston,
Phys. Rev. Lett. 111, 047001 (2013).
We report investigations of the structural, magnetic, electrical transport, and thermal properties of five compositions of the metallic perovskite GdRh3C1-xBx (0.00 ≤ x ≤ 1.00). Our results show that all five compositions undergo magnetic ordering at low temperatures, but the nature of the ordered state is significantly different in the carbon- and the boron-rich compositions, where the former shows signatures of an amplitude-modulated magnetic structure and the latter exhibits evidence of an equal-moment incommensurate antiferromagnetic ordering. We also observe a remarkable field-dependent evolution of conduction carrier polarization in the compositionally disordered compounds. The outcomes indicate that this system is energetically situated in proximity to a magnetic instability where small variations in the control parameter(s), such as the lattice constant and/or electron density, lead to considerably different ground states.
Abhishek Pandey, A. K. Singh, Shovan Dan, K. Ghosh, I. Das, S. Tripathi, U. Kumar, R. Ranganathan, D. C. Johnston, and Chandan Mazumdar,
Phys. Rev. Materials 4, 084411 (2020).
