Magnetism in dilute magnetic oxide thin films based on SnO2
Magnetism in dilute magnetic oxide thin films based on SnO2
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DOI：
10.1103/physrevb.74.115307
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发表时间：
2006-09-01
影响因子：
3.7
通讯作者：
Sias, U. S.
中科院分区：
文献类型：
--
作者：
Fitzgerald, C. B.;Venkatesan, M.;Sias, U. S.
采用脉冲激光沉积技术在R切割蓝宝石衬底上制备的SnO2薄膜，当掺入铬、锰、铁、钴、镍而不掺入其它3d阳离子时，在室温下表现出铁磁性。外推的居里温度一般在500K以上。薄膜的温度与掺杂水平大致无关，从0.1-15at。%，每单位衬底面积的值为200+/-100亩(B)nm(-2)。当磁化强度表示为每3d掺杂离子的磁矩时，它的变化范围从低浓度下大于纯自旋的值到渗流阈值附近的小于0.2mU(B)/离子。铁的价值最高。薄膜的磁化强度是高度各向异性的，当磁场垂直于衬底时，磁化强度是面内磁化强度的两倍以上。除了高掺杂水平外，几乎没有磁滞现象。该氧化物为简并n型半导体，其霍尔迁移率为100 cm(2)V-1 S(-1)和1.4×10(19)载流子cm(-3)，但在室温下没有观察到反常的霍尔效应和磁阻。这些数据与(A)半导体中铁磁性的施主杂质带模型和(B)磁缺陷模型有关。
Thin films of SnO2 prepared by pulsed-laser deposition on R-cut sapphire substrates exhibit ferromagnetic properties at room temperature when they are doped with Cr, Mn, Fe, Co, or Ni, but not with other 3d cations. Extrapolated Curie temperatures are generally in excess of 500 K. The moment of the films is roughly independent of doping level, from 0.1-15 at. %, with a value per unit substrate area of 200 +/- 100 mu(B) nm(-2). When magnetization is expressed as a moment per 3d dopant ion, it varies from more than the spin-only value at low concentrations to less than 0.2 mu(B)/ion near the percolation threshold. Greatest values are found for iron. The magnetization of the films is highly anisotropic with values when the field is applied perpendicular to the substrate more than double the in-plane values. There is little hysteresis except at high doping levels. The oxides are degenerate n-type semiconductors with a Hall mobility of 100 cm(2) V-1 s(-1) and 1.4x10(19) carriers cm(-3) in a one-band model, but no anomalous Hall effect or magnetoresistance was observed at room temperature. The data are discussed in relation to (a) the donor impurity-band model of ferromagnetism in semiconductors and (b) the magnetic defect model.