Magnetic Domain and Bubble Structures Observed on Fe/Co Crossed Wedge
Yao-Jui Chan1*, Chih-Heng Huang1, Liang-Wei Lan1, Chun-I Lu2, Tzu-Hung Chuang2, Chii-Bin Wu3, Der-Hsin Wei2, Chien-Cheng Kuo1
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Department of Physics, Chung Yuan Christian University, Taoyuan, Taiwan
* Presenter:Yao-Jui Chan,
Tailoring the domain structures in magnetic ultrathin film, such as stripe domain, vortex structure, and chirality of domain wall configurations, has attracted a lot of attention because of their application on the technologies of high-density data-storage and low power consumed spintronic devices. These spin textures are the result of the competition between the exchange energy, magnetic anisotropic energy, dipolar energy, and the interaction at the interface of magnetic heterostructures which usually depend on the thickness of magnetic ultrathin films. A deeper insight into the domain configurations with thickness is thus crucial for searching these exotic spin textures. Here, we address this issue through observing the evolution of magnetic domains of a specially designed crossed structure of Fe/Co wedge by the photoemission electron microscopy (PEEM) with circularly polarized X-rays. The influence of Fe film on the evolution of Co domains was clearly seen. We observed an additional transition region, beyond spin orientation transition (SRT) region of Co and Fe film, with intricate domain structures and bubble-like domain with tiny size at the area with the 3.3 to 4.0 ML Co which is capped by 2.6 to 3.2 ML Fe. Zooming into the domain images, it shows that bubble structures have with asymmetric domain shape and domain contrast, suggesting it has vortex-like spin configuration. These vortex are attributed the non-collinear interaction and competition between the Neel wall and Bloch wall in area with the in-plane magnetization. On the other hand, we also observed the shifting of critical thickness of SRT region with Fe thickness. This shifting is due to the contributing magnetic bulk anisotropy of Fe and Co as a whole, causing the transition happened at less Co thickness. These observations provide us the opportunity to engineer the domain size and domain shape by tailoring the thickness distribution of the magnetic heterostructures.

Keywords: spin reorientation transition, magnetic domain evolution, photoemission electron microscopy