Laguta V V, Kamba S, Maryško M, Andrzejewski B, Kachlík M, Maca K, Lee J H, Schlom D G
Institute of Physics ASCR, Na Slovance 2, 18221 Prague 8, Czechia. Institute of Physics, Opole University, Oleska 48, 45-052 Opole, Poland.
J Phys Condens Matter. 2017 Mar 15;29(10):105401. doi: 10.1088/1361-648X/aa58c6. Epub 2017 Jan 11.
Magnetic resonance spectra of EuTiO in both bulk and thin film form were taken at temperatures from 3-350 K and microwave frequencies from 9.2-9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin-spin interactions were determined: the exchange frequency is 10.5 GHz and the estimated critical exponent of the spin correlation length is ≈0.4. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the Néel temperature, T ≈ 5.5 K, while the resonance field practically does not change even on cooling below T . This is indicative of a small magnetic anisotropy ~320 G in the antiferromagnetic phase. In the film, the magnetic resonance spectrum is split below T into several components due to excitation of the magnetostatic modes, corresponding to a non-uniform precession of magnetization. Moreover, the film was observed to degrade over two years. This was manifested by an increase of defects and a change in the domain structure. The saturated magnetization in the film, estimated from the magnetic resonance spectrum, was about 900 emu cm or 5.5 µ /unit cell at T = 3.5 K.
对块状和薄膜形式的EuTiO的磁共振谱在3 - 350 K的温度以及9.2 - 9.8 GHz和34 GHz的微波频率下进行了测量。在顺磁相中，磁共振谱由Eu自旋之间的磁偶极和交换相互作用决定。在薄膜中，退磁场起了很大作用。通过对线宽及其温度依赖性的详细分析，确定了自旋 - 自旋相互作用的参数：交换频率为10.5 GHz，自旋关联长度的估计临界指数约为0.4。在块状样品中，谱在奈尔温度T≈5.5 K处线宽呈现出明显的最小值，而即使冷却到T以下，共振场实际上也没有变化。这表明在反铁磁相中磁各向异性较小，约为320 G。在薄膜中，由于静磁模式的激发，磁共振谱在T以下分裂为几个分量，这对应于磁化的非均匀进动。此外，观察到薄膜在两年内发生退化。这表现为缺陷增加和畴结构变化。从磁共振谱估计，薄膜在T = 3.5 K时的饱和磁化强度约为900 emu/cm³或5.5 µB/晶胞。
