Grain boundaries as the controlling factor for the ferromagnetic behaviour of Co-doped ZnO

Straumal, Boris B.; Мазилкин, А. А.; Protasova, S. G.; Straumal, P. B.; Myatiev, A. A.; Schütz, Gisela; Goering, E.; Tietze, Thomas; Baretzky, B.

doi:10.1080/14786435.2012.736693

Cited by 105 publications

(69 citation statements)

References 118 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since all three samples are known to be paramagnetic, the presence of the defects cannot be associated with magnetic order, as speculated previously. 11 The extrinsic stacking faults that are present in each Co:ZnO layer introduce regions of both compressive and tensile strain into the wurtzite structure. The stacking fault densities in the RMS and PLD deposited films are in the 10 17 cm À3 range (Table I).…”

Section: Discussionmentioning

confidence: 99%

“…5,8 The need for high-spatial resolution studies of DMS materials, such as doped ZnO is even more important in view of the recent proposals that ferromagnetism in these materials may be related to the presence of structural defects. 10,11 Here, we make use of recent advances in aberrationcorrected TEM and optimized specimen preparation techniques for TEM to study the structure and chemistry of Co:ZnO layers that have been deposited onto c-plane sapphire using two common preparation techniques: pulsed laser deposition (PLD) and reactive magnetron sputtering (RMS). We use a combination of scanning TEM (STEM) imaging and electron energy-loss spectroscopy (EELS) to characterize grain boundaries, planar defects and interfaces in order to reveal structural features and possible chemical inhomogeneities, some of which have not been previously reported in transition-metaldoped oxides.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

Kovács

Ney

Duchamp

et al. 2013

Journal of Applied Physics

View full text Add to dashboard Cite

Room-temperature ferromagnetic Co-doped ZnO nanoneedle array prepared by pulsed laser deposition Appl. Phys. Lett. 87, 173119 (2005) We study planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al 2 O 3 ), as well as the Co:ZnO/Al 2 O 3 interface, using aberration-corrected transmission electron microscopy and electron energy-loss spectroscopy. Co:ZnO samples that were deposited using pulsed laser deposition and reactive magnetron sputtering are both found to contain extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers next to the Al 2 O 3 substrate. The stacking fault density is in the range of 10 17 cm À3 . We also measure the local lattice distortions around the stacking faults. It is shown that despite the relatively high density of planar defects, lattice distortions, and small compositional variation, the Co:ZnO films retain paramagnetic properties. V C 2013 AIP Publishing LLC.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

Kovács

Ney

Duchamp

et al. 2013

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…Therefore, the magnetic moments can not be increased by increasing the fluence of irradiation all the time, while, the amount of paramagnetic centers can be scaled up with neutron fluence and show saturation at very large fluences. The locally accumulation of ferromagnetic defects has also been suggested for defective ferromagnetic oxides [14,19,79].…”

Section: (A)mentioning

confidence: 99%

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

et al. 2015

View full text Add to dashboard Cite

Defect-induced ferromagnetism has triggered a lot of investigations and controversies. The major issue is that the induced ferromagnetic signal is so weak that it can sufficiently be accounted for by trace contamination. To resolve this issue, we studied the variation of the magnetic properties of SiC after neutron irradiation with fluence covering four orders of magnitude. A large paramagnetic component has been induced and scales up with defect concentration, which can be well accounted for by uncoupled divacancies. However, the ferromagnetic contribution is still weak and only appears in the low fluence range of neutrons or after annealing treatments. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: a higher defectconcentration favors a larger magnetic interaction at the expense of spin polarization. Combining both experimental and first-principles calculation results, the defect-induced ferromagnetism can probably be understood as a local effect which cannot be scaled up with the volume. * Electronic address: s.zhou@hzdr.de 2

show abstract

“…The role of GB in promoting RTFM in ZnO is suggested in the experimental studies. 2,3,17 Magnetic force microscopy has predicted that intrinsic and extrinsic defects at GBs can be the origin of the FM observed in Mn doped ZnO thin films. 17 However, the contribution of GBs in ZnO in promoting RTFM is not studied in detail and can be understood only through a systematic and microscopic study that incorporates varied concentrations of point defects at the GBs.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4] The realization of these technologies depends on the development of room temperature ferromagnetism (RTFM) in ZnO. Even though doping ZnO with transition metals (TMs) is a widely employed technique, 5 many studies failed to reproduce the long-range RTFM.…”

Section: Introductionmentioning

confidence: 99%

Defect induced d ferromagnetism in a ZnO grain boundary

Aravindh

Schwingenschloegl

Roqan

2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

Several experimental studies have referred to the grain boundary (GB) defect as the origin of ferromagnetism in zinc oxide (ZnO). However, the mechanism of this hypothesis has never been confirmed. Present study investigates the atomic structure and the effect of point defects in a ZnO GB using the generalized gradient approximation+U approximation. The relaxed GB possesses large periodicity and channels with 8 and 10 numbered atoms having 4 and 3 fold coordination. The Zn vacancy (V Zn ) shows a tendency to be attracted to the GB, relative to the bulk-like region. Although no magnetization is obtained from point defect-free GB, V Zn induces spin polarization as large as 0.68 µ B /atom to the O sites at the GB. Ferromagnetic exchange energy >150 eV is obtained by increasing the concentration of V Zn and by the injection of holes into the system. Electronic structure analysis indicates that the spin polarization without external dopants originates from the O 2p orbitals, a common feature of d 0 semiconductors. C 2015 AIP Publishing LLC. [http://dx

show abstract

Grain boundaries as the controlling factor for the ferromagnetic behaviour of Co-doped ZnO

Cited by 105 publications

References 118 publications

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

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

Defect induced d ferromagnetism in a ZnO grain boundary

Contact Info

Product

Resources

About