Eur. Phys. J. B (2013) 86: 148
https://doi.org/10.1140/epjb/e2013-31094-4

Regular Article

Magnetic properties of the multiferroic chromium thio-spinels CdCr₂S₄ and HgCr₂S₄

¹ Department of Physics and Astronomy, Uppsala University, 75121 Uppsala, Sweden
² Physics Department, Technische Universität München, 85747 Garching, Germany
³ Experimental Physics V, Center for Electronic Correlations and Magnetism, Universität Augsburg, 86159 Augsburg, Germany
⁴ Institute of Applied Physics, Academy of Sciences, 2028 Chisinau, Republic of Moldova

^a e-mail: vladimir.tsurkan@physik.uni-augsburg.de

Received: 5 December 2012
Received in final form: 1 February 2013
Published online: 10 April 2013

Abstract

Powder samples of CdCr₂S₄ and HgCr₂S₄ were investigated with respect to their magnetic behavior using muon spin rotation/relaxation spectroscopy (μSR). In CdCr₂S₄, a second order magnetic transition at 83 ± 1 K is confirmed. No influence on the μSR magnetic parameters due to the simultaneous ferroelectric transition was detected. In the limit T → 0, persistent spin fluctuation exists as a consequence of magnetic frustration. The proposed structural transition around 150 K is barely visible in the μSR spectra, indicating that the change in local symmetry is subtle. In HgCr₂S₄, we see in zero field at 27 ± 2 K a second order transition from the paramagnetic into a long-range ordered (LRO) magnetic state. This LRO state is characterized in the μSR spectra by a spontaneous spin precession signal. Applications of moderate magnetic fields (up to 450 mT) destroy the precession signal in favor of a rapidly decaying exponential signal. It reflects short-range order (SRO) of strongly correlated dynamic spins. The magnitude of the field required to induce this change is dependent on temperature. The observation of an increase of magnetic spin fluctuations with applied field suggests that spin dynamics play a key role in the field induced changes of the magnetic properties.