Akihiko IKEDA (池田 暁彦)

In strong magnetic fields beyond 100 T, the significant Zeeman energy competes with the lattice interactions, where a considerable magnetostriction is expected. However, the microscopic observation of the magnetostriction above 100 T has been hindered due to the short pulse duration of microseconds and the coil’s destruction. Here, we report the observation of the giant and anisotropic magnetostriction of ∼ 1 % at 110 T in the spin-controlled crystal β − O 2 by combining the single-shot diffraction of an x-ray free-electron laser (XFEL) and the newly developed portable 100 T generator (PINK-02). The soft and anisotropic response of β − O 2 should originate in the competing van der Waals force and exchange interaction and also the frustration of spin and lattice on the triangular network. The XFEL experiment above 100 T using PINK-02 enables microscopic investigations on materials’ properties at high magnetic fields, providing insights into how spins contribute to the stability of crystal structures.

The underlying symmetry of the crystal, electronic structure, and magnetic structure manifests itself in the anisotropy of materials' properties, which is a central topic of the present condensed matter research. However, it demands such a considerable effort to fill the explorable space that only a small part has been conquered. We report a vector pulse magnet (VPM) as an alternative experimental technique to control the direction of applied magnetic fields, which may complement the conventional methods with its characteristic features. The VPM combines a conventional pulse magnet and a vector magnet. The VPM can create vector-pulsed magnetic fields and swiftly rotating-pulsed magnetic fields. As a demonstration, the three-dimensional magnetoresistance measurement of a highly oriented pyrolytic graphite is carried out using the AC four-probe method at 4.5 K and 6 T. The two-dimensional electronic structure of graphite is visualized in the three-dimensional magnetoresistance data. One can uncover the rotational and time-reversal symmetry of materials using a VPM and a variety of measurement techniques.

There is a growing interest in using pulsed high magnetic field as a controlling parameter of physical phenomena in various scientific disciplines, such as condensed matter physics, particle physics, plasma physics, chemistry, and biological studies. We devised a concise and portable pulsed magnetic field generator that produces a 40 T field with a pulse duration of 2 ms. It is assembled using only off-the-shelf components and a homemade coil that leverages small computers, Raspberry Pi, and Python codes. It allows for straightforward modification for general purposes. As working examples, we show representative applications in condensed matter experiments of magnetoresistance, magnetization, and magnetostriction measurements for graphite, NdNi2P2, and NdCo2P2, respectively, with the maximum magnetic field of 41 T and the lowest temperature of 4.2 K.