Evidence of Oxygen Ferromagnetism in ZnO Based Materials

Abstract

Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

“…In ZnO, the origin of the local moment is more complicated. Both Zn and O vacancies have been suggested to be responsible for the induced magnetism [18,[60][61][62]. On the other hand, oxygen atoms on the polar ZnO surface can be spin polarized and undergo a long-range magnetic interaction [63][64][65].…”

Magnetic and optical properties of Co-doped ZnO nanocrystalline particles

“…It has a wide band gap of 3.37 eV, a large exciton binding energy of 60 meV, high electron mobility and thermal conductivity, and a large piezoelectric constant. The theoretical prediction of room temperature ferromagnetism (RTFM) in transition metal (TM) doped ZnO [3,4], the observation of ferromagnetism in un-doped ZnO [5,6], and in TMdoped ZnO, e.g., Mn-doped ZnO [7e11], Ni-doped ZnO [12e14], and Co doped ZnO [15,16,17,18] has opened up the possibility to use these diluted magnetic semiconductors (DMS) in magneto-optics and magneto-electronics (spintronics) technologies. Following the prediction and the observation of RTFM in TM-doped ZnO, many research groups has performed different magnetic studies on these DMS.…”

Advances in methods to obtain and characterise room temperature magnetic ZnO

“…[1][2][3][4][5][6] However, there is now consent that the origin of the magnetically ordered state in diluted oxide semiconductors is related to lattice defects and/or added ions, which are not necessarily magnetic, a phenomenon called defect-induced magnetism. [7][8][9][10][11][12][13] Nevertheless, in spite of the large number of experimental studies, there is no simple method to introduce systematically the required defect concentration in the corresponding lattice sites. Moreover, low resistivity and magnetic p-type oxides, necessary for further implementation in electronic devices, remain an unresolved goal partially because of the formation of oppositely charged defects, which pin the Fermi level.…”