Multiferroicity in Li0.05Ti0.02Ni0.93O Above Room Temperature

Abstract

We present direct evidence of above room temperature magneto-electricity in single-phase Li0.05Ti0.02Ni0.93O with above-ambient antiferromagnetic ordering. Temperature-hysteresis in warming/cooling heat-flow thermograms establishes a discontinuous/first-order nature of the cubic-to-rhombohedral structural change concurring the AFM transition. At TN = 488K, magnetization features a sharp slope-&-curvature discontinuity and dielectric constant shows a peak-anomaly. Room temperature P-E loop measures a large polarization traceable to the N\`eel domain walls. We find positive room-temperature magneto-capacitance up to 9T, linear at low-fields (MC ~ Hlow); the prefactor slope (dln{\epsilon}'/dHlow) featuring a positive frequency-coefficient rises from O(10-3/T) at 0.1MHz to O(10-1/T) at 4MHz, with maximum d{\epsilon}'/dH ~ 120/T.