Takuo Ohkochi at PEEM Workshop 2021

FOCUS PEEM in SPring-8 designed for magnetic dynamics study with synchrotron radiation

Takuo Ohkochi

Japan Synchrotron Radiation Research Institute (JASRI)

Abstract

In the synchrotron radiation facility, SPring-8, we newly installed FOCUS PEEM in 2017 [1] and now it has routinely been used in domestic / public experimental subjects. Previously, we had complementary used two types of PEEM machines. One is a spectroscopic low-energy/photoemission electron microscope (LEEM III, ELMITEC GmbH) at a-branch of BL17SU RIKEN soft X-ray beamline, which has dedicated to high resolvution and static imaging. Another PEEM (PEEMSPECTOR, ELMITEC GmbH) had been utilized in BL25SU soft X-ray beamline as a versatile machine whose resolving power was moderate but useful for experiments under extreme situations (e.g. time-resolved measurements, imaging under applied external fields), thanks to its simple optics structure. However, since the performance of PEEMSPECTOR has been deteriorated due to long-term use, the FOCUS PEEM installed at b-branch of BL17SU is now succeeding its role as a higher-end machine. In our FOCUS PEEM system, instead of adopting integral sample (IS) stage (which is very convenient for laboratory experiments with fixed research targets), we independently constructed a high-stiffness six-axis (X, Y, X-tilt, Y-tilt, Z, and f) sample manipulator, in order to cope with samples of various shapes and experimental conditions. A robust manipulator body attached to a stiff carved chamber offers a highly stable measurement environment, with which an achieved spatial resolution of an image with mercury lamp was 36.7 nm.

Figure 1: (a) 6-axis manipulator equipped in our FOCUS PEEM system. (b)Lase-pulse induced giant spin waves discovered in Gd22Fe70Co8 ferrimagnetic thin film observed by time-resolved XMCD-PEEM (Gd M5).

In the talk, I introduce specifications of our PEEMs and light sources available in our soft X-ray beamline, previous scientific achievements with a focus on time-resolved magnetic structures analyses such as an observation of gigantic spin waves in the process of pulsed laser irradiation to ferrimagnetic thin films [2], and future outlook of magnetic dynamics studies using the FOCUS PEEM such as observations of nucleation process of micron-sized magnetic vortices, as well as technical development plans.


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References

[1] T. Ohkochi et al., Jpn. J. Appl. Phys, 58, 118001 (2019).

[2] T. Ohkochi et al., Appl. Phys. Express 10, 103002 (2017).

Speaker Info

Dr. Takuo Ohkochi completed his doctorate in science at Kyoto University in 2006 with the research focused on the magnetism study of multilayered-film materials investigated by X-ray magnetic scattering and Mössbauer spectroscopy. He worked as a postdoctral researcher in Japan Atomic Energy Agency/SPring-8 from 2006 to 2009, in charge of soft X-ray spectroscopy of strongly-correlated materials. From 2009, he joined in Japan Synchrotron Radiation Research Institute/SPring-8 as a research scientist and dedicating to a variety of materials studies using photoemission electron microscopy. In 2018, he became a senior scientist of the same institute and now he is continuing the same research.

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