Role of local short-scale correlations in the mechanism of negative magnetization

Abstract

We elaborate here why the antiferromagnetically ordered GdCrO${}_3$ responds in a diamagnetic way under certain conditions, by monitoring the evolution of the microscopic global and local magnetic phases. Using high energy $\sim$ 0.3 eV neutrons, the magnetic ordering is shown to adopt three distinct magnetic phases at different temperatures: G${}_x^{Cr}$,A${}_y^{Cr}$,F${}_z^{Cr}$ below Néel temperature = 171 K; (F${}_x^{Cr}$, C${}_y^{Cr}$, G${}_z^{Cr}$)$\bullet$( F${}_x$${}^{Gd}$,C${}_y$${}^{Gd}$) below 7 K and an intermediate phase for 7 K $\le T\le$ 20 K in the vicinity of spin-reorientation phase transition. Although, bulk magnetometry reveals a huge negative magnetization (NM) in the terms of both magnitude and temperature range ( $M_{-max}$ ( 18 K)$\sim$ 35 $\times M_{+max}$ (161 K), $\hat{I}”T\sim 110$ K in presence of $\hat{I}{¼}_{0}H$ = 0.01 T); the long-range magnetic structure and derived ordered moments are unable to explain the NM. Real-space analysis of the total (Bragg's + diffuse) scattering reveals significant magnetic correlations extending up to $\sim$ 9 $\tilde{A}$. Accounting for these short-range correlations with a spin model reveals spin frustration in the S= 3 ground state, comprising competing first, second and third next nearest exchange interactions with values J${}_1$ = 2.3 K, J${}_2$ = -1.66 K and J${}_3$ = 2.19 K in presence of internal field, governs the observance of NM in GdCrO${}_3$.

11 pages, 8 figures