Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 5: Spin Structures and Magnetic Phase Transitions
MA 5.6: Talk
Monday, March 26, 2012, 10:45–11:00, H 0112
High-field magnetism and magneto-acoustics in UCo2Si2 — •S. Yasin1, A.V. Andreev2, Y. Skourski1, S. Zherlitsyn1, and J. Wosnitza1 — 1Dresden High Magnetic Field Laboratory, Helmholtz- Zentrum Dresden-Rossendorf, 01314 Dresden, Germany — 2Institute of Physics ASCR, Na Slovance 2, 18221 Prague 8, The Czech Republic
We report results of magnetization and magneto-acoustic studies on a UCo2Si2 single crystal in high magnetic fields. This compound orders antiferromagnetically at the Néel temperature TN = 83 K and shows at low temperatures a first-order metamagnetic transition (MT) at 45 T with very small hysteresis (µ0Δ Hcr = 0.16 T) to a ferrimagnetic state seen as a sharp jump in the magnetization when the magnetic field is applied along the c direction. The magnetization curve measured along the a axis shows no transition and is linear up to 60 T. The acoustic properties exhibit drastic anomalies in the vicinity of both magnetic phase transitions; the spontaneous and the field-induced one. At TN, a pronounced change in the sound velocity Δv/v accompanied with a peak in the attenuation Δ α has been observed. Whereas Δ α only shows a very sharp peak at the MT, Δv/v displays a more complicated behavior; it has a non-monotonous temperature evolution with maximum effects at 30 K, which can be due to the transition changing from first to second order. Our results enabled us to map the phase diagram of UCo2Si2 in fields applied along the c axis. We discuss our observations in relation to the magnetism on the U site and the magneto-elastic interaction in this material. *Part of this work was supported by EuroMagNET under the EU contract No. 228043.