Field-induced incommensurate-to-commensurate transition in Ba_2CuGe_2O_7

TL;DR

This paper reports the experimental observation of a magnetic phase transition in Ba_2CuGe_2O_7 induced by an external magnetic field, supported by neutron diffraction and analytical modeling.

Contribution

It provides the first experimental evidence of a field-induced incommensurate-to-commensurate transition in a Dzyaloshinskii-Moriya spiral antiferromagnet, with quantitative agreement to theoretical models.

Findings

Transition occurs at critical field Hc=2.1T

Magnetic structure period and magnetization match analytical solutions

Experimental results confirm Dzyaloshinskii's model predictions

Abstract

We report an observation of a commensurate-incommensurate phase transition in the Dzyaloshinskii-Moriya spiral antiferromagnet Ba_2 Cu Ge_2 O_7. The transition is induced by an external magnetic field applied along the c-axis of the tetragonal structure, i. e., in the plane of spin rotation. Bulk magnetic measurements and neutron diffraction experiments show that the transition occurs in a critical field Hc=2.1T. Experimental results for the period of the magnetic structure and magnetization as functions of magnetic field are in quantitative agreement with our exact analytical solution for Dzyaloshinskii's model of commensurate-incommensurate transitions in spiral magnets.