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TT 3.11: Vortrag
Montag, 16. März 2020, 12:15–12:30, HSZ 201
Low-Energy Excitations in NiTiO3 and Ni0.25Mn0.75TiO3 Probed by Antiferromagnetic Resonance — •Martin Jonak, Kaustav Dey, Johannes Werner, Changhyun Koo, and Rüdiger Klingeler — Kirchhoff Institute of Physics, Heidelberg University, Heidelberg, Germany
We study magnetic excitations in NiTiO3 and Ni0.25Mn0.75TiO3 by means of X-band and high-frequency electron spin resonance spectroscopy. Our data for NiTiO3 show that in the antiferromagnetically ordered and spin-reoriented phase, i.e. below TN and in external magnetic fields above the spin-reorientation field BC = 1.13(8) T, antiferromagnetic resonance (AFMR) modes are well described by a two-sublattice model with an easy ab-plane. Correspondingly, two zero-field excitation gaps are deduced at Δ1 ≈ 15 GHz and Δ2 = 185(2) GHz, respectively. At B < BC, an additional magnon mode is observed, which rules out a simple two-sublattice model, thereby contradicting the presently established picture of the low-field ground state. The strongly Mn-doped Ni0.25Mn0.75TiO3 exhibits at least two antiferromagnetically ordered phases. The low-temperature phase shows AFMR modes of a two-sublattice antiferromagnet with anisotropy gaps Δ1 = 29(1) GHz and Δ2 = 139(3) GHz.