Coherent Resonant Soft X-ray Scattering Study of Magnetic Textures in FeGe

Victor Ukleev,Daisuke Morikawa,Taka-Hisa Arima,Hironori Nakao,Yoshihiro Okamura,Naoya Kanazawa,Yuichi Yamasaki,Yoshinori Tokura

doi:10.3390/qubs2010003

Abstract

Coherent resonant soft X-ray scattering was utilized to examine the magnetic textures in a thin plate of the cubic B20 compound FeGe. Small-angle scattering patterns were measured with controlled temperatures and magnetic fields exhibiting magnetic scattering from a helical texture and skyrmion lattice. By measuring the scattering pattern in a saturation magnetic field, magnetic and charge scattering were distinguished and an iterative phase retrieval algorithm was applied to reconstruct the magnetic texture in the real-space. Results of the real-space reconstruction of magnetic texture from two independently measured datasets were used to compare the reliability of the retrieval.

Highlights

Lensless imaging with coherent hard and soft X-rays is a rapidly developing technique, which has been successfully performed in various studies in the fields of nanotechnology, biology, and condensed matter physics [1]
Soft X-ray imaging is a complementary technique to Lorentz transmission electron microscopy (LTEM) which is sensitive to the in-plane magnetic flux inside the sample and produces no contrast in the case of Néel-type skyrmions [45,46,47], which has been recently observed in magnetic ultra-thin films [48,49,50] and bulk polar magnets [51,52,53,54]
We can suggest that the inequality between the skyrmion and the helical texture periodicities in FeGe samples reported in a previous resonant soft X-ray scattering experiment [14] has been induced by the tensile strain due to the tungsten contacts that were used to attach the specimen to the Si3N4 substrate [63]

Summary

Introduction

Lensless imaging with coherent hard and soft X-rays is a rapidly developing technique, which has been successfully performed in various studies in the fields of nanotechnology, biology, and condensed matter physics [1]. Dichroic resonant soft X-ray scattering can be successfully combined with coherent diffraction approaches such as iterative phase retrieval [17,18,19], Fourier transform holography-based methods [20,21,22,23], and ptychography [24,25] for the lensless real-space imaging of local magnetic moment at the scale from a few tens of nanometers to a few microns. We employed a phase retrieval algorithm to reconstruct the lensless images of the magnetic textures from the coherent small-angle resonant soft X-ray scattering (RSXS) patterns measured from the magnetically ordered compound FeGe. The magnetic phase diagram of B20-type non-centrosymmetric cubic FeGe has been extensively studied for bulk crystals [32,33], thin plates [14,34], and epitaxial films [35,36,37,38,39,40]. Soft X-ray imaging is a complementary technique to LTEM which is sensitive to the in-plane magnetic flux inside the sample and produces no contrast in the case of Néel-type skyrmions [45,46,47], which has been recently observed in magnetic ultra-thin films [48,49,50] and bulk polar magnets [51,52,53,54]

Materials and Methods

Experiment

Results and Discussion

Conclusions