Hemberger J, Rudolf T, Krug von Nidda H-A, Mayr F, Pimenov A, Tsurkan V, Loidl A
Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany.
Phys Rev Lett. 2006 Aug 25;97(8):087204. doi: 10.1103/PhysRevLett.97.087204. Epub 2006 Aug 22.
Magnetic susceptibility, specific heat, thermal expansion, and IR spectroscopy provide experimental evidence that the two subsequent antiferromagnetic transitions in ZnCr2S4 at TN1 = 15 K and TN2 = 8 K are accompanied by significant thermal and phonon anomalies. The anomaly at TN2 reveals a temperature hysteresis typical for a first-order transformation. Because of strong spin-phonon coupling, both magnetic transitions at TN1 and TN2 induce a splitting of phonon modes. The anomalies and phonon splitting observed at TN2 are suppressed by strong magnetic field. Regarding the small positive Curie-Weiss temperature Theta approximately 8 K, we argue that this scenario of two different magnetic phases with different magnetoelastic couplings results from the strong competition of ferromagnetic and antiferromagnetic exchange.
磁化率、比热、热膨胀和红外光谱提供了实验证据，表明ZnCr2S4中在TN1 = 15 K和TN2 = 8 K发生的两个相继的反铁磁转变伴随着显著的热异常和声子异常。TN2处的异常揭示了一级相变典型的温度滞后现象。由于强的自旋-声子耦合，TN1和TN2处的两个磁转变都导致声子模式的分裂。在TN2处观察到的异常和声子分裂被强磁场抑制。关于约8 K的小的正居里-外斯温度θ，我们认为这种具有不同磁弹耦合的两个不同磁相的情况是由铁磁和反铁磁交换的强烈竞争导致的。
