High temperature magnetism and charge ordering in multiferroic (LuFeO3)m/(LuFe2O4)1 (m = 3, 7, 9)

KEVIN ARTHUR SMITH; HENA DAS; SHIYU FAN; ALEJANDRO RÉBOLA

Congreso; APS March Meeting 2020; 2020

American Physical Society

We combined optical spectroscopy, magnetic circular dichroism, and first principles calculations to uncover the microscopic origin of the high temperature magnetism in multiferroic superlattices (LuFeO3)m/(LuFe2O4)1, as well as the charge ordered state in the m = 3 case. Analysis of the dichroic spectra at characteristic energies reveals optical hysteresis loops of different Fe centers. Comparison between coercivity vs temperature curves indicates the bulk magnetization emanates mostly from the LuFe2O4 layer. Spectroscopic signature of the interface demonstrates that the larger Lu distortion only selectively increases the local magnetization of the Fe2+ and Fe3+ sites in the spin-up channel, which strengthens the exchange interaction, increases the total magnetization in the LuFe2O4 layer and enhances TC. Comparison between the calculated and measured dichroic spectra affirms a non-polar charge ordered state in the (3, 1) case. These findings provide a site specific technique to analyze the complex interactions in the materials with multiple magnetic centers, and also broaden the possibilities in the hunt for novel multiferroics with high TC and large magneto-electric coupling constant.