Ferromagnetic domain nucleation and growth in colossal magnetoresistive manganite
Ferromagnetic domain nucleation and growth in colossal magnetoresistive manganite
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DOI：
10.1038/nnano.2009.342
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发表时间：
2010-01-01
影响因子：
38.3
通讯作者：
Tonomura, A.
中科院分区：
文献类型：
--
作者：
Murakami, Y.;Kasai, H.;Tonomura, A.
巨磁电阻是由外加磁场引起的电阻率急剧下降（1-4），由于其在磁性数据存储方面的潜力，如使用锰矿石等材料，它一直是许多研究的焦点。尽管广泛的显微镜和理论研究（5-11）表明，巨大的磁电阻涉及相互竞争的绝缘相和铁磁导电相，但这种效应的机制尚不清楚。在这里，通过使用低温洛伦兹显微镜和电子全息术直接观察磁畴壁和通量分布（12-14），我们证明了外加磁场有助于有序铁磁相的成核和生长。这些结果为纳米尺度下复杂结构的演化动力学提供了新的见解，并有助于解释与应用相关的异常相分离现象（3,15-19）。我们的方法还可以用于确定纳米级区域的磁性参数，如磁晶各向异性和交换刚度，而无需体磁化结果或中子散射数据。
Colossal magnetoresistance is a dramatic decrease in resistivity caused by applied magnetic fields(1-4), and has been the focus of much research because of its potential for magnetic data storage using materials such as manganites. Although extensive microscopy and theoretical studies(5-11) have shown that colossal magnetoresistance involves competing insulating and ferromagnetic conductive phases, the mechanism underlying the effect remains unclear. Here, by directly observing magnetic domain walls and flux distributions using cryogenic Lorentz microscopy and electron holography(12-14), we demonstrate that an applied magnetic field assists nucleation and growth of an ordered ferromagnetic phase. These results provide new insights into the evolution dynamics of complex domain structures at the nanoscale, and help to explain anomalous phase separation phenomena that are relevant for applications(3,15-19). Our approach can also be used to determine magnetic parameters of nanoscale regions, such as magneto-crystalline anisotropy and exchange stiffness, without bulk magnetization results or neutron scattering data.