Temperature Dependence of Complex Relative Permeability of the Polycrystalline La0.7Sr0.3MnO3

Abstract

<p>吾人量測多晶態鑭鍶錳氧變化溫度的電阻率與頻率範圍為 10 kHz 至 10 MHz 的相對複數磁導率特性。樣品室溫電阻率很小，僅為數 m⋅Ωcm。電阻率隨著溫度增加，在相轉變溫度 TP = 361 K 附近顯現金屬到半導體的相轉變。室溫量測到的磁譜顯現與磁壁位移有關的鬆弛特性，色散情況非常明顯。隨著溫度升高，磁導率增加，在居禮溫度 TC前達到最大值，然後迅速下降。當溫度從室溫增加，磁壁位移鬆弛頻率 fr幾乎保持不變。當溫度升高到 TC附近，由於磁導率迅速降低，fr劇烈增加。在 TC以上，磁譜的色散現象消失。量測到的 fr與理論值相當符合，可看出磁壁位移的阻滯來源主要源自於渦電流阻滯。</p> <p> </p><p>The temperature-dependent resistivity and complex relative permeability of the polycrystalline La0.7Sr0.3MnO3 have been investigated in the frequency range 10 kHz -10 MHz. The measured room-temperature resistivity is of the order of mcm. As the temperature increases, the resistivity increases and shows a metal-insulator transition. The transition temperature TP is about 361 K. There are pronounced dispersions of the relaxation in the measured spectra, which are due to the domain-wall displacement. The magnitude of permeability increases with increasing temperature, reaches its maximum value near the Curie temperature TC, and then abruptly drops. As the temperature increases, the relaxation frequency fr almost remains a constant value. However, it rapidly increases around TC due to the suddenly decrease of the permeability. The dispersion phenomena of the permeability spectra disappear above TC. The consistence of the measured and calculated fr value shows that the damping factor of domain-wall displacement mainly comes from the eddy current.</p> <p> </p>