Local short-scale correlations and the origin of negative magnetization*

Negative Magnetization (NM) defined as the opposite alignment of net magnetization with respect to applied magnetic field in magnetically ordered systems has been associated with a number of unsettled debates regarding the origin and reliability of this phenomena. The presence of two highly neutron absorbing isotopes of natural Gd has prevented to understand the microscopic magnetic structure and consequently the microscopic outlook of NM in GdCrO_3, so far. We have utilized λ = 0.4994Å hot neutrons, a value much higher than the resonance energy, to record the thermal evolution of neutron diffraction patterns. Using magnetic pair distribution function analysis, significant local short range Gd³⁺ correlations in disordered state are observed ranging upto ~9 Å. Calculations suggest the frustated S= 3 ground state of locally ordered Gd ions with competing FM- AFM exchange interactions and states corresponding to NM are comparitively more stablized. The extermely small excitation gap between energy levels is argued to be resonsible for the different spin state populations characterized by distinct kinetic rates corresponding to cooling and warming cycles, which explains the observed path dependency of NM in GCO.