The origin of ferromagnetism and defect-magnetization correlation in nanocrystalline ZnO

Emergent ferromagnetism in ZnO/Al2O3 core-shell nanowires: Towards oxide spinterfaces

“…Because the sample contains multiple compositions, we cannot accurately determine the magnetism in terms of formula unit. Nevertheless, the observed value of saturation magnetization in A-AZO is comparable to what reported for nanograined ZnO films (0.05 emu/g), 12 but much higher than those of undoped ZnO nanoparticles obtained via chemical routes (between 0.0015 and 0.0022 emu/g) 40,41 and ZnO nanorods (0.004 emu/g), 42 as well as the thiol-capped ZnO nanoparticles (0.003 emu/g). 20 To find out the origin of magnetism in the annealed ZnO/Al 2 O 3 core-shell NWs, we measured a control sample of ZnAl 2 O 4 nanocrystals, which were fabricated using the conventional solid stat reaction route from high-purity ZnO and Al 2 O 3 powders, and found that ZnAl 2 O 4 nanocrystals exhibits only a diamagnetic behavior [ Fig.…”

Fluctuant magnetism in metal oxide nanocrystals capped with surfactants

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Ferromagnetism (FM) can be induced in non-magnetic metal oxide NCs by a variety of methods or factors. For example, intrinsic defects such as oxygen or cation vacancies in pure metal oxides (such as ZnO, CeO 2 , or SnO 2 ) can lead to room temperature (RT) FM.…”

“…For example, intrinsic defects such as oxygen or cation vacancies in pure metal oxides (such as ZnO, CeO 2 , or SnO 2 ) can lead to room temperature (RT) FM. [2][3][4][5] Defects intentionally induced by doping nonmagnetic elements (such as Ti and V) into metal oxides can also produce RT FM. 6 A more traditional method is doping magnetic impurities (such as Co, Ni, Mn, and Cr) to introduce magnetic moments directly.…”

Room-temperature ferromagnetism in Zn1−xMnxO

“…On the other hand, it has been observed, recently, that by annealing at around 500 1 C one can introduce oxygen vacancies in the ZnO system [14][15][16], which makes it ferromagnetic at room temperature in its nanocrystalline phase [15]. In a recent work, Sundaresan et al [17] observed room temperature ferromagnetism in nanoparticles of nonmagnetic oxides such as CeO 2 , Al 2 O 3 , ZnO, In 2 O 3 and SnO 2 .…”

“…Recently, a number of experiments showed the correlation between ferromagnetic behavior and concentration of structural defects, either Zn interstitials [21] or oxygen vacancies [14,15,22] incorporated into the ZnO host lattice giving an evidence that ferromagnetism in ZnO:Mn is mediated by donor-bound carriers. The presence of oxygen vacancies or interstitial zinc possibly results in an increase of conductivity since they may create donor electrons [13], while a large amount of cationic defect or excess of dopant can also lead to cluster or secondary phases.…”