Laboratoire Matériaux et Phénomènes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, 75205 Paris cedex 13, France.
Phys Rev Lett. 2011 Jul 8;107(2):027202. doi: 10.1103/PhysRevLett.107.027202. Epub 2011 Jul 5.
We have studied the impact of the magnetic field on the electromagnon excitations in TbMnO₃ crystal. Applying a magnetic field along the c axis, we show that the electromagnons transform into pure antiferromagnetic modes, losing their polar character. Entering in the paraelectric phase, we are able to track the spectral weight transfer from the electromagnons to the magnon excitations and we discuss the magnetic excitations underlying the electromagnons. We also point out the phonons involved in the phase transition process. This reveals that the Mn-O distance plays a key role in understanding the ferroelectricity and the polar character of the electromagnons. Magnetic field measurements along the b axis allow us to detect a new electromagnon resonance in agreement with a Heisenberg model.
我们研究了磁场对 TbMnO₃ 晶体中电磁激元激发的影响。通过沿 c 轴施加磁场，我们发现电磁激元转变为纯反铁磁模式，失去了其极性特征。进入顺电相时，我们能够跟踪从电磁激元到磁激元激发的光谱权重转移，并讨论了电磁激元所涉及的磁激发。我们还指出了相变过程中涉及的声子。这表明 Mn-O 距离在理解铁电性和电磁激元的极性特征方面起着关键作用。沿 b 轴的磁场测量允许我们检测到一个新的与海森堡模型一致的电磁激元共振。
