Defect-induced magnetism in SiC

Abstract

Defect induced magnetism, which can be controllably generated by ion or neutron irradiation, is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC samples. In combination with X-ray absorption spectroscopy, high-resolution transmission electron microscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture. For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals. With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [5]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: Defects favor spin polarization at the expense of magnetic interaction. Although both Raman scattering and X-ray diffraction reveal essential structure damage to SiC due to irradiation, high-resolution transmission electron microscopy does not detect significant structural variation even upon the largest neutron fluence.

F+ center exchange mechanism and magnetocrystalline anisotropy in Ni-doped 3C-SiC

“…However, it has been reported in the literature as well as observed by us that even pure 3C-SiC display ferromagnetic response at RT due to defects present in it [23]. But the magnetic moment value is at least 3 orders of magnitude smaller than that of the Ni-doped samples.…”

“…As pure SiC exhibits defect-induced weak magnetism which cannot scale into the entire volume, there have been studies on p-type carrier doping to enhance the strength of d 0 magnetism. In addition to introducing p-type carriers if the dopant also carries a magnetic moment then it may be an added advantage [20][21][22][23][24].…”

Precise Regulation of Carrier Concentration in Thermoelectric BiSbTe Alloys via Magnetic Doping

“…Xiao et al reported that the intrinsic antisite defects resulted in the magnetism in Bi 2 Te 3 . As reported in the literatures, − magnetism can be induced by lattice defects in many materials, which is called “defect-induced magnetism” or “d 0 magnetism”. Furthermore, with the doping of FM elements, intrinsic vacancies could strengthen the coupling between FM dopants, leading to an enhanced FM ordering .…”

Influence of the Crystallinity of Silver Nanoparticles on Their Magnetic Properties

“…The subject is heavily documented in the case of oxides, nitrides and semiconductors, for thin films or nano-objects (e. g., nanoparticles, tubes, ribbons, …). [30][31][32] The most common cases are oxygen or nitrogen vacancies. Carbon vacancies or 'dangling bonds' in materials such as graphene are also known to induce magnetism.…”

“…There are examples of materials becoming magnetic upon presence of extrinsic ( e. g ., Fe atoms in Pt) or intrinsic defects. The subject is heavily documented in the case of oxides, nitrides and semiconductors, for thin films or nano‐objects ( e. g ., nanoparticles, tubes, ribbons, …) [30–32] . The most common cases are oxygen or nitrogen vacancies.…”