Site dependent localized-delocalized magnetic moment in the magnetization-reversal in an inverse-spinel vanadate
ORAL
Abstract
Neutron diffraction, magnetization, and muon spin relaxation measurements, complemented by density functional theory (DFT) calculations are employed to unravel the various magnetic phases of the inverse spinel Co2VO4. All measurements show a second-order magnetic phase transition at TC = 168 K to a colinear ferrimagnetic phase. DFT and the experimental results indicate the moments in the ferrimagnetic phase are delocalized and undergo gradual localization as the temperature is lowered below TC . The delocalized-localized crossover gives rise to a maximum magnetization at TNC = 138 K with a continuous decrease in the magnetization and sign-change at TMR= 65 K. The magnetization reversal determined at zero fields is found to be highly sensitive to an applied magnetic field, such that above B= 0.03 T, instead of a reversal, a minimum in the magnetization is apparent at TMR. Analysis of the neutron diffraction measurements shows that the magnetization reversal is due to a gradual change in the-nearly ferromagnetic A and B sub-lattices that grow differently as the temperatures are lowered below TC. Muon measurements are consistent with the picture that the moments gradually become more localized as the temperature is lowered and at that at zero applied magnetic fields give rise to magnetization reversal or a minimum (at applied magnetic fields) at TMR.
*Part of this research at Ames Laboratory is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Contract No. DE-AC02-07CH11358. The electronic structure and magnetism employed in this work are developed in the Critical Materials Institute, an Energy Innovation Hub led by the Ames Laboratory and funded by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. Use of the Spallation Neutron Source at the Oak Ridge National Laboratory is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Scientific Users Facilities Division. Experiments at the ISIS Pulsed Neutron and Muon Source were supported by a beamtime allocation from the Science and Technology Facilities Council. We thank the Helmholtz-Zentrum Berlin for the allocation of neutron beamtimes at BER II and bulk properties measurements at CoreLab Quantum Materials.
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Publication:Magnetization reversal driven by site-dependent magnetic moment fluctuations in inverse spinel Co$_{2}$VO$_{4}$.
