ABSTRACT
Half-metallic fully compensated ferrimagnets (HM-FCFMs) constitute a special class of half-metals exhibiting zero magnetization at zero temperature. While there have been a number of theoretical studies predicting the existence of such materials over the last 25 years, very few of those have been synthesized and observed that they exhibit expected properties. Herein, we demonstrate that a NiAs-type hexagonal-structured (CrFe)S compound could serve as an HM-FCFM material. It has a half-metallic nature of 100% spin-polarised Fermi surfaces and yet zero magnetisation at the ground state. The magnetisation shows linear behaviour as a function of the magnetic field at temperatures below the compensation temperature (~ 190 K). In addition, it shows a high magnetic coercivity of 3.8 T at 300 K. These magnetic features contribute to a significant development in the application of HM-FCFMs for spintronics devices.
ABSTRACT
Co2MnGa is a Weyl semimetal exhibiting giant anomalous Hall and Nernst effects. Using spin-polarized positron annihilation spectroscopy, we examined a Bridgman-grown Co2MnGa single crystal with a nearly perfectL21-ordered structure and a reference Co2MnAl polycrystal with a Mn-Al-disorderedB2 structure. We found that a large amount of magnetic vacancies (more than 100 ppm) were included in the Co2MnGa crystal but not the Co2MnAl crystal. We discuss possible reasons for the inclusion of vacancies, the role of vacancies in the development of the ordered structure, and the electronic states associated with the vacancies. Toward the development of Co2MnGa-based devices, the manners for reducing vacancies as well as the influence of vacancies on the electrical transport properties should be considered.
ABSTRACT
Band-gap engineering is one of the fundamental techniques in semiconductor technology and also applicable in next generation spintronics using the spin degree of freedom. To fully utilize the spintronic materials, it is essential to optimize the spin-dependent electronic structures in the operando conditions by applying magnetic and/or electric fields. Here we present an advanced spectroscopic technique to probe the spin-polarized electronic structures by using magnetic circular dichroism (MCD) in resonant inelastic soft X-ray scattering (RIXS) under an external magnetic field. Thanks to the spin-selective dipole-allowed transitions in RIXS-MCD, we have successfully demonstrated the direct evidence of the perfectly spin-polarized electronic structures for the prototypical halfmetallic Heusller alloy [Formula: see text]. RIXS-MCD is a promising tool to probe the spin-dependent carriers and band-gap induced in the buried magnetic layers in an element specific way under the operando conditions.
ABSTRACT
The magnetization distribution in Co2FeSi which has the largest moment per formula unit â¼6 µB of all Heusler alloys, has been determined using polarized neutron diffraction. The experimentally determined magnetization has been integrated over spheres centred on the three sites of the L12 structure giving µ Fe = 3.10(3) µB and µ Co = 1.43(2) µB, results which are slightly lower than the moments in atomic spheres of similar radii obtained in recent LDA + U band structure calculations (Li et al 2010 Chin. Phys. B 19 097102). Approximately 50% of the magnetic carriers at the Fe sites were found to be in orbitals with eg symmetry. This was higher, ≃65%, at the Co sites. Both Fe and Co were found to have orbital moments that are larger than those predicted. Comparison with similar results obtained for related alloys suggests that there must be a finite density of states in both spin bands at the Fermi energy indicating that Co2FeSi is not a perfect half-metallic ferromagnet.
ABSTRACT
DC and AC magnetic measurements were carried out to clarify the difference in the magnetic ground state depending on the kinds of Z element used in the martensite phase in Ni-Mn-Z (Z = In, Sn and Sb) off-stoichiometric Heusler alloys. Magnetic field cooling effects were observed in the DC thermomagnetization curves in the low temperature regions, and a frequency dependence on AC susceptibility was also observed in both real and imaginary parts of the susceptibility. Negative divergence was clearly observed in nonlinear AC susceptibility only for the Ni(50)Mn(40)Sb(10) alloy, suggesting that the magnetic feature of its ground state is the spin-glass state. The magnetic ground state of the martensite phase in these alloys would relate to the magnetic configuration of the Mn atoms in the ferromagnetic austenite phase.
