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HL: Fachverband Halbleiterphysik

HL 4: Complex Oxides: Bulk Properties (jointly with DS, HL, KFM, MA, O) (joint session TT/HL/MA)

HL 4.11: Vortrag

Montag, 16. März 2020, 12:15–12:30, HSZ 201

Low-Energy Excitations in NiTiO₃ and Ni_0.25Mn_0.75TiO₃ 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 Ni_0.25Mn_0.75TiO₃ 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 T_N and in external magnetic fields above the spin-reorientation field B_C = 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 < B_C, 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 Ni_0.25Mn_0.75TiO₃ 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.