Terahertz Spin Wave Resonances and Crystal Field Transitions in RCrO3 (R=Pr, Sm, Er) at Ultra Low Temperatures

NESTOR E. MASSA; KARSTEN HOLLDACK; RODOLPHE SOPRACASE; VINH TA PHUOC,; LEIRE DEL CAMPO; DOMINGOS DE SOUSA MENESES; PATRICK ECHEGUT; JOSE A. ALONSO

Ciudad Autonoma de Buenos Aires

Workshop; Multifunctional Oxides: Synergy between fundamental science and novel technologies.; 2017

Comision Nacioanl de Energia Atomica

Aiming to understand spin wave resonances1 in polycrystalline RCrO3 (R=Pr, Sm, Er) we show that spin reorientation temperature TSR is determinant on ferromagnetic-like (FM) spin modes and antiferromagnetic-like (AFM) being optically active. We also report on crystal field level temperature and field dependences. Pr3+ non-Kramers lowest energy main transition emerges at 100 K. The no detection of spin wave resonances is attributed to Pr3+ remaining paramagnetic disrupting Cr3+-Pr3+ exchanges. In SmCrO3 we propose magnetic compensation as for not detecting Sm3+ ground state transitions. The FM and AFM harden upon lowering temperature and split linearly on applied fields at 5 K. In ErCrO3 the Er3+ Kramers doublet becomes active at ~TSR onset. Each Zeeman line splits further under magnetic fields. The field-induced spin reversal at ~1.5 T yields a secondary split at the highest Zeeman level. The Γ2 5 K AFM and FM magnetic excitations show concerted frequency-intensity temperature dependence. A shoulder in the AFM profile points to subtle distortions by Er3+ smaller ion at the A site. An even more convoluted behavior is found when both modes merge into an induced continuum prompted by the external field. At 2 K, in the Γ1 representation, the resonances reduce to one excitation. 1.F. Keffer and C. Kittel. Phys. Rev. 85, 329 (1952); ); G. F. Herrmann. Phys. Rev. 133, A1334 (1964)