Magnetic anisotropy of BaCu2Si2O7: theory and antiferromagnetic resonance

TL;DR

This paper investigates the magnetic anisotropy and antiferromagnetic resonance of BaCu2Si2O7, revealing two energy gaps and spin re-orientation transitions, with a microscopic theory attributing these features to Hund's rule coupling.

Contribution

It provides a microscopic theory explaining the magnetic anisotropy and AFMR gaps in BaCu2Si2O7, highlighting Hund's rule coupling as a key factor.

Findings

Two AFMR gaps at 40 and 76 GHz observed at 4.2 K

Identification of spin re-orientation transitions for H||c

Hund's rule coupling causes residual anisotropy

Abstract

Antiferromagnetic resonance (AFMR) of BaCu2Si2O7 and a microscopic theory of the magnetic anisotropy of spin 1/2 chain compounds with folded CuO3 geometry being in good agreement with the available data are presented. The AFMR studies at 4.2 K show the existence of two gaps (40 and 76 GHz) at zero magnetic field and of two spin re-orientation transitions for H||c. The microscopic origin of the two gaps is shown to be Hund's rule coupling which leads to a "residual anisotropy" beyond the compensation of the Dzyaloshinskii-Moriya term by the symmetric anisotropy which would be valid without Hund's coupling.