PtSn by complementary microscopy and scattering experiments using LTEM and REXS

More than a decade has passed since the first experimental evidence of magnetic Bloch-type skyrmions in MnSi [1]. Meanwhile, driven by basic research interests in topologically protected magnetic nanostructures and their potential for applications in future magnetic memory devices, skyrmions and related magnetic objects of non-trivial topology have been intensively studied. In the course of these efforts, antiskyrmions (aSks) were recently observed in the tetragonal Heusler material Mn_1.4PtSn by Lorentz Transmission Electron Microscopy (LTEM). This material is also known to host a wide range of other magnetic structures such as non-topological (NT) bubbles, elliptical skyrmions and spin helices [3].

In order to better understand the formation of aSks we have conducted complementary experiments of resonant elastic x-ray scattering (REXS) and LTEM on an identical lamella of Mn_1.4PtSn. The setup of the REXS experiment included an octupole vector magnet that allowed to explore the highly complex magnetic phase diagram of Mn_1.4PtSn by offering 360 degrees of freedom in magnetic field direction and field stregths of up to 600 mT. This allowed us to determine the orientation and magnitude of the spin propagation vectors of the various magnetic phases in Mn_1.4PtSn in-situ as function of the magnitude and orientation of an external magnetic field. While REXS yields diffraction and scattering patterns, the complimentary LTEM investigation allow for a direct imaging and identification of the underlying magnetic structures and to navigate dynamically the material’s complex phase diagram, which depends not only on temperature and sample shape, but also on strength and orientation of an external magnetic field as well as on the history of its application.

Our study allows us to unambiguously link the helical phase, NT bubble and aSks phase in Mn_1.4PtSn as identified from LTEM measurements to the REXS scattering patterns measured on the identical sample. In combination with a quantitative analysis of the REXS patterns the investigations provide new insights into the field-driven magnetic phase transitions in the material.

 

Reference(s):

[1] S. Mühlbauer et al., Science. 323, 915-919 (2009).

[2] A.K. Nayak et al., Nature. 548, 561 (2017).

[3] L. Peng et al., Nature Nanotechnol. 15, 181-186 (2020).