Weak ferrimagnetism and multiple magnetization reversal in {\alpha}-Cr3(PO4)2

TL;DR

This study investigates the weak ferrimagnetic behavior and complex magnetization reversals in {lpha}-Cr3(PO4)2, revealing temperature-sensitive magnetic phenomena linked to its crystal structure and magnetic interactions.

Contribution

It provides the first detailed analysis of the weak ferrimagnetism and multiple magnetization reversals in {lpha}-Cr3(PO4)2, highlighting the role of structural inequivalence and magnetic frustration.

Findings

{lpha}-Cr3(PO4)2 has a Curie temperature of 29 K.

The compound exhibits multiple temperature-induced magnetization reversals.

X-ray spectra confirm high-spin divalent chromium ions.

Abstract

The chromium(II) orthophosphate {\alpha}-Cr3(PO4)2 is a weak ferrimagnet with the Curie temperature TC = 29 K confirmed by a \lambda-type peak in specific heat. Dominant antiferromagnetic interactions in this system are characterized by the Weiss temperature {\Theta} = - 96 K, indicating an intermediate frustration ratio |{\Theta}|/TC ~ 3. In its magnetically ordered states {\alpha}-Cr3(PO4)2 exhibits a remarkable sequence of temperature-induced magnetization reversals sensitive to the protocol of measurements, i.e. either field-cooled or zero-field-cooled regimes. The reduction of the effective magnetic moment 4.5 {\mu}B/Cr2+, as compared to the spin-only moment 4.9 {\mu}B/Cr2+, cannot be ascribed to the occurence of the low-spin state in any crystallographic site of the Jahn-Teller active 3d4 Cr2+ ions. X-ray absorption spectra at the K-edge indicate divalent chromium and unravel the high-spin state of these ions at the L2,3-edges. Weak ferrimagnetism and multiple magnetization reversal phenomena seen in this compound could be ascribed to incomplete cancellation and distortion of partial spontaneous magnetization functions of Cr2+ in its six crystallographically inequivalent positions.