Giant shifts of crystal-field excitations with temperature as consequence of internal magnetic exchange fields

Joel O'Brien; Guochu Deng; Dehong Yu; Xiaoxuan Ma; Zhenjie Feng; Wei Ren; Shixun Cao; Robert A. Robinson; Garry J. McIntyre; Clemens Ulrich

arXiv · 2109.04610

Giant shifts of crystal-field excitations with temperature as consequence of internal magnetic exchange fields

Joel O'Brien·Guochu Deng·Dehong Yu·Xiaoxuan Ma·Zhenjie Feng·Wei Ren·Shixun Cao·Robert A. Robinson·Garry J. McIntyre·Clemens Ulrich

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Abstract

Crystal-field excitations, for example in transition-metal oxides where a rare-earth element is used as a spacer between the transition-metal-oxide tetrahedra and octahedra, are assumed to be extremely robust with respect to external perturbations such as temperature. Using inelastic neutron scattering experiments, a giant shift of the energy of the lowest crystal-field excitation of Er3+ (4I15/2) in ErFeO3 from 0.30(2) meV to 0.75(2) meV was measured below the magnetic-ordering temperature of erbium at 4.1 K. Quantum-mechanical point-charge calculations of the crystal-field levels indicate that the shift is caused by the internal magnetic field created by the erbium spins themselves, which causes a Zeeman splitting of the erbium 4f electronic levels, and therefore a change in the energies of crystal-field transitions. To verify this explanation, the effect of an external magnetic field on the crystal-field excitations was measured by inelastic neutron scattering and compared to the field-dependent point-charge calculations. The existence of an internal magnetic exchange interaction will have implications for a deeper understanding of a broader group of phenomena such as multiferroic properties or spin frustration, which are a consequence of various competing electronic and magnetic exchange interactions.

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Joel O'Brien, Guochu Deng, Dehong Yu, Xiaoxuan Ma, Zhenjie Feng, Wei Ren, Shixun Cao, Robert A. Robinson, Garry J. McIntyre, Clemens Ulrich. 2021-09-10. Giant shifts of crystal-field excitations with temperature as consequence of internal magnetic exchange fields. https://arxiv.org/abs/2109.04610

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