Study of spin-phonon interaction in multiferroic La0.9Bi0.1CrO3 by Raman spectroscopy

Abstract

Spin-phonon interaction is an interesting phenomenon that may find applications in spintronics, quantum information processing, etc. In multiferroic materials, spin-phonon interaction, if exists, may provide additional degrees of freedom that could lead to the development of novel technologies. Thus, investigating and understanding this interaction in a multiferroic material is of both fundamental and applied interests. Perovskite La1-xBixCrO3 is a mutiferroic material which turns from antiferromagnetic/antiferroelectric to ferromagnetic/ferroelectric with 10 % substitution of Bi3+ for La3+. Raman spectrum feature changes dramatically with 10 % substitution of Bi3+ for La3+ also, indicating a spin-phonon interaction. Furthermore, in La0.9Bi0.1CrO3, the ∼700 cm−1 mode is split into two Raman sub-modes. The intensity of the lower frequency (680 cm−1) sub-mode starts increasing sharply around the Néel temperature TN = 269 K upon cooling. Below TN, the monotonic change in intensity reflects the magnetic exchange modulation, resulted from the interacting with the chromium atoms oscillation at the original Cr4+ position in LaCrO3, related to the competing ferromagnetic and antiferromagnetic interactions, with the former prevailing at low temperatures. The interplay of magnetic exchange modulation interactions and chromium atoms oscillation (decreasing of the lower frequency sub-mode of the Bi3+ doping related John-Teller-like 700 cm−1 mode) coincides with the corresponding magnetic phase transition (TN), demonstrating a spin-phonon coupling in La0.9Bi0.1CrO3 which may find applications in magnonic devices.