Measurement of X-ray Magnetic Linear Dichroism by Rotating Polarization Angle of Soft X-ray Generated by a Segmented Cross Undulator

X-ray magnetic linear dichroism (XMLD) is a widely used technique to probe magnetic anisotropy. By measuring absorption while changing the relative angle between crystalline axes and the linear polarization of soft X-rays, one can obtain information about spin orientation of magnets. Due to limitation in the polarization control of soft X-rays, XMLD measurements have conventionally been conducted by rotating samples about a certain axis. Here, we report a new method for XMLD measurements that is realized by continuously rotating the linear-polarization angle using a segmented cross undulator. Through interference of right-and left-handed circularly polarized light, linear polarization is generated at an arbitrary angle. We present a successful demonstration of this XMLD measurement method applied to the antiferromagnet NiO. The new technique will be particularly useful for operando measurements of non-uniform samples where sample size and rotational motion are severely restricted.