Magneto-structural Quantum Phases and Reentrant Magnetic Behavior of Few Complex Spinels

Date

Jul 16, 2015

Time

10:00 AM - 11:00 AM

Speaker

Dr. Subhash Thota

Affiliation

Indian Institute of Technology Guwahati (IIT Guwahati), Indien

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Brit Präßler-Wüstling

Description

Magnetic spinels, generally isostructural with the mineral spinel MgAl2O4, are considered as important class of materials because of their potential applications such as in microwave-wave devices, transformer cores, actuators, thermistors and magnetic recording. Such applications of magnetic spinels (AB2O4) combined with the interesting physics resulting from a variety of distributions of magnetic ions between the tetrahedral ‘A’-sites and octahedral ‘B’-sites has kept the field of spinels a very active area of research for many decades. Therefore, the current talk is focused on two types of spinels namely (i) Hausmannite (Mn3O4) and (ii) Cobalt Ortho-Stannate & Titanates (Co2TiO4 & Co2SnO4,) which belong to tetragonally distorted spinels and inverse-spinel family, respectively.1-4 Special emphasis will be given to Hausmannite which exhibits giant-atomic-displacement associated with enormous magnetocrystalline anisotropy, strong magneto-dielectric coupling, and giant magnetic-entropy change at the onset of the ferrimagnetic Néel temperature. During the first-half of the talk, the low-temperature magnetostructural quantum phases of Mn3O4 system will be discussed in the light of our recent experimental findings.1,3 The second part of the talk will be focused on the reentrant magnetic behavior of two inverse spinels Co2SnO4 and Co2TiO4. Both of these systems exhibit co-existence of longitudinal ferrimagnetic order below the Néel temperature TN = 41K (for Co2SnO4) and transverse spin-glass (SG) state below TSG  = 39.1 K (Co2SnO4) resulting from the presence of non-magnetic Sn4+ ions (or Ti4+) on the B sites.2,4 The origin of ferrimagnetic ordering in both the systems is suggested to result from different magnetic moments of Co2+ on the A sites (3.87 μ B) and B sites (4.16 μ B).4 The temperature variation of ac-magnetic susceptibilities (χ′(T) and χ″(T)), and antiferromagnetic molecular field constants together with the exchange-constants of both the inverse spinels will be discussed. The effect of various doping elements on the global magnetic structure of Co2TiO4 , Co2SnO4 and Mn3O4 will be investigated at IFW-Dresden. References: [1] M. Kim et. al, Phys. Rev. Lett. 104, 136402 (2010). [2] S. Thota et. al. J. Phys.: Condens. Matter, 27, 166001 (2015) [3] F. Guillou, et. al. Phys. Rev. B, 83, 094423, (2011) [4] S. Thota et al. J. Appl. Phys. 113, 203905 (2013)

Links

• Seminars at the IFW

Last modified: Jul 16, 2015, 10:00:40 AM