Abstract:
X-ray magnetic circular dichroism (XMCD) spectroscopy is a key technique to study the magnetic materials, providing the element specificity and the significantly high detection sensitivity of magnetic moments. The XMCD technique can be combined with the sophisticated X-ray focusing optics so that scanning magnetic microscopy using a circularly-polarized X-ray nanoprobe will become feasible. In SPring-8, we have developed XMCD spectroscopy and magnetic microscopy/imaging techniques in the soft and hard X-ray regions [1]. In this talk, the instrumentation developments at dedicated soft X-ray (BL25SU) and hard X-ray (BL39XU) undulator beamlines are described. These beamlines offer the capability of fast helicity switching of the circularly polarized X-ray beam with the high-sensitive lock-in detection of dichroic signals. A partial X-ray fluorescence detection mode has been implemented for in-situ soft-XMCD spectroscopy of buried magnetic layers in spintronic devices with an application of a voltage bias. For magnetic imaging, BL25SU is equipped with a Fresnel zone plate for a scanning soft-XMCD microscopy with a spatial resolution of 100 nm and under strong magnetic fields by a unique combination of an 8-T-superconducting magnet [2]. BL39XU is equipped with a Kirkpatrick-Baez mirror setup for scanning hard-XMCD microscopy with the resolution of 100 nm [3]. We present our recent highlights including an XMCD study of voltage-induced magnetic anisotropy in transition metal/MgO junctions [4, 5], observation of the evolution of magnetic domains of bulk Nd-Fe-B permanent magnet [6], and three-dimensional visualization of internal magnetic domains via hard-X-ray magnetic microtomography [7].