Paul Scherrer Institut, Villigen PSI, CH-5232 Switzerland.
Phys Rev Lett. 2010 Mar 26;104(12):127201. doi: 10.1103/PhysRevLett.104.127201. Epub 2010 Mar 24.
Using photoemission electron microscopy, we study the magnetization orientation in single 5-25 nm iron particles coupled to a ferromagnetic cobalt support. We find a noncollinear alignment between the particle and substrate magnetization above a particle size of approximately 6 nm and a parallel alignment for smaller sizes. Numerical calculations reveal a transition from an exchange-dominated to an anisotropy-dominated regime on increasing the particle height: the smaller particles are in a single-domain collinear state while larger particles exhibit a spin-spiral magnetic structure determined by the magnetic anisotropy energy.
利用光电子发射电子显微镜，我们研究了与铁磁钴基底耦合的单个 5-25nm 铁颗粒中的磁化方向。我们发现，当颗粒尺寸大于约 6nm 时，颗粒与基底磁化之间呈非共线排列，而在较小尺寸时则呈平行排列。数值计算表明，随着颗粒高度的增加，从交换主导转变为各向异性主导：较小的颗粒处于单畴共线状态，而较大的颗粒则表现出由磁各向异性能决定的螺旋磁结构。
