We explore two methods for single-crystal growth of the theoretically proposed magnetic Weyl semimetals RAlGe (R = Pr, Ce), which prove that a floating-zone technique, being both crucible-and flux-free, is crucial to obtain perfectly stoichiometric RAlGe crystals. In contrast, the crystals grown by a flux-growth technique tend to be Al-rich. We further present both structural and elemental analyses, along with bulk magnetization and electrical resistivity data on the crystals prepared by the floating-zone technique. Both systems with the intended 1:1:1 stoichiometry crystallize in the anticipated polar I4 1 md (No. 109) space group, although neither displays the theoretically expected ferromagnetic ground state. Instead PrAlGe displays a spin-glass-like transition below 16 K with an easy c axis and CeAlGe has an easy-ab-plane antiferromagnetic order below 5 K. The grown crystals provide an ideal platform for microscopic studies of the magnetic field-tunable correlation physics involving magnetism and topological Weyl nodes.

We report a vortex-like magnetic configuration in uniaxial ferromagnet Fe3Sn2 nanodisks using differential phase contrast scanning transmission electron microscopy. This magnetic configuration is transferred from a conventional magnetic vortex using a zero-magnetic-field warming process and is characterized by a series of concentric cylinder domains. We termed them as “target bubbles” that are identified as three-dimensional depth-modulated magnetic objects in combination with numerical simulations. Target bubbles have room-temperature stability even at zero magnetic field and multiple stable magnetic configurations. These advantages render the target bubble an ideal bit to be an information carrier and can advance magnetic target bubbles toward functionalities in the long term by incorporating emergent degrees of freedom and purely electrically controllable magnetism.

While in most ferro or antiferromagnetic materials there is a unique crystallographic direction, including crystallographically equivalent directions, in which the moments like to point due to spinorbit coupling, in some, the direction of the spin reorients as a function of a certain physical parameter such as temperature, pressure etc. Fe3Sn2 is a kagome ferromagnet with an onset of ferromagnetism below 650 K, and undergoes a spin reorientation near 150 K. While it is known that the moments in Fe3Sn2 point perpendicular to the kagome plane at high temperatures and parallel to the kagome plane at low temperatures, how the distribution of the magnetic domains in the two different spin orientations evolve throughout the spin reorientation is not well known. Furthermore, while there have been various reports on the magnetotransport properties in the Hall configuration, the angular dependence of magnetoresistance has not been studied so far. In this paper, we have examined the spin reorientation by using anisotropic magnetoresistivity in detail, exploiting the dependence of the resistivity on the direction between magnetization and applied current. We are able to determine the distribution of the magnetic domains as a function of temperature between 360 K to 2 K and the reorientation transition to peak at 120 K. We discover that both out of plane and in plane phases coexist at temperatures around the spin reorientation, indicative of a first order transition. Although the volume of the magnetic domains in the different phases sharply changes at the spin reorientation transition, the electronic structure for a specific magnetization is not influenced by the spin reorientation. In contrast, we observe an electronic transition around 40 K, hitherto unreported, and reflected in both the zero-field resistivity and anisotropic resistivity. Introduction:Kagome Fe3Sn2 orders ferromagnetically below a Curie temperature of TC = 640 K based on SQUID magnetometry [1]. Previous studies using Mossbauer spectroscopy reported a Curie temperature of 612 K[2] and 657 K [3]. Below the ordering temperature, the easy axis of magnetization is parallel to the crystallographic c-axis. Initial study using Mossbauer spectroscopy noticed that a transition (SRT) occurs at 114 K[2]. Following studies using Mossbauer spectroscopy suggested that below 220 K, there are abrupt spin rotations occurring over a large temperature range 0-220 K with the spin direction close to the ab Kagome plane at low temperatures [3]. Further studies investigating the spin rotation using neutron diffraction combined with Mossbauer spectroscopy noted that the rotation is more complicated than a continuous rotation described by a unique angle or a simple abrupt rotation [4].The spin reorientation transition (SRT) was recently revisited, using powder neutron diffraction, where the transition was suggested to occur over a large temperature range from 570 K to 75 K[1]. The order of the transition is not discussed in any of the previous reports and they report very broad tr...

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We report differential phase contrast scanning transmission electron microscopy (TEM) of nanoscale magnetic objects in Kagome ferromagnet Fe3Sn2 nanostructures. This technique can directly detect the deflection angle of a focused electron beam, thus allowing clear identification of the real magnetic structures of two magnetic objects including three-ring and complex arch-shaped vortices in Fe3Sn2 by Lorentz transmission electron microscopy imaging. Numerical calculations based on real material-specific parameters well reproduced the experimental results, showing that the magnetic objects can be attributed to integral magnetizations of two types of complex three-dimensional (3D) magnetic bubbles with depth-modulated spin twisting. Magnetic configurations obtained using the high-resolution TEM are generally considered as two-dimensional (2D) magnetic objects previously. Our results imply the importance of the integral magnetizations of underestimated 3D magnetic structures in 2D TEM magnetic characterizations.