Field induced antiferromagnetism and $^{17}$O Knight shift anomaly in La$_2$CuO$_4$

TL;DR

This paper investigates how external magnetic fields induce antiferromagnetism in La$_2$CuO$_4$ and how $^{17}$O NMR Knight shift anomalies reveal the role of Dzyaloshinsky-Moriya interactions in cuprates.

Contribution

It demonstrates that $^{17}$O Knight shift measurements can effectively probe field-induced antiferromagnetism and Dzyaloshinsky-Moriya coupling effects in cuprates.

Findings

Field induced antiferromagnetism observed in La$_2$CuO$_4$

Anisotropic antiferromagnetic contributions explain NMR anomalies

Potential method to determine Dzyaloshinsky vector orientation

Abstract

We address the effect of the field induced antiferromagnetism in paramagnetic state of the cuprate weak ferromagnet La$_2$CuO$_4$. The planar oxygen $^{17}$O Knight shift is shown to be an effective tool to inspect the effects of Dzyaloshinsky-Moriya coupling in cuprates in an external magnetic field. Field induced antiferromagnetism and anisotropic antiferromagnetic contribution to $^{17}$K explain the anomalies observed in $^{17}$O NMR in La$_2$CuO$_4$. The experimental observation of antiferromagnetic contribution to the $^{17}$O Knight shift provides probably the only way to find out the problem of the sense of Dzyaloshinsky vector in cuprates.