Who
Tathamay Basu, Michigan State University
Abstract
In this talk, I will briefly discuss intriguing magnetic and magnetoelectric behavior of some strongly correlated magnetic systems. As a proto-type example, an unconventional spin-driven ferroelectricity in GdCrTiO5, originating from a metastable magnetic field-induced canting of Chromium sublattice in the presence of Gadolinium moments, will be presented. A distinct spin-driven ferroelectric order is revealed below 11 K only after application of magnetic field (H>10 kOe), despite of any signature of (H-induced) magnetic ordering in bulk magnetic susceptibility, which is unusual. The spectroscopic (μSR) investigation confirms a weak magnetic ordering of Cr below 11 K in zero magnetic field. We have systematically investigated another system, 6H-perovskites Ba3RRu2O9 (R= Nd, Sm, Tb and Ho). Our results evidence the gradual enhancement of magnetodielectric coupling with the introduction of heavier R-ions in this series. We have performed comprehensive neutron powder diffraction measurements for the compound Ba3HoRu2O9. We report cooperative magnetic ordering of Ru and Ho moments below ~ 50 K (TN1), attributable to strong 4d(Ru)-4f(R) magnetic correlation, followed by another magnetic phase transition ~10 K (TN2). The latter one is associated with phase co-existence of two different magnetic phase, which suggests complex magnetism in this system arising from competing magnetic interaction of Ru and Ho-moments. The spin-driven ferroelectricity arises due to exchange stiction of up-up-down-down magnetic structure, associated with the emerging magnetic phase below TN2. Ref.: [1] T. Basu, et al., Phys. Rev. B 96, 184431 (2017) [2] T. Basu, et al., Phys. Rev. Materials 3, 114401 (2019) [3] T. Basu, et al., arXiv:2005.10861
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