Crystallographically oriented Co and Ni nanocrystals inside ZnO formed by ion implantation and postannealing

Abstract

In the last decade, transition-metal-doped ZnO has been intensively investigated as a route to room-temperature diluted magnetic semiconductors (DMSs). However, the origin for the reported ferromagnetism in ZnO-based DMS remains questionable. Possible options are diluted magnetic semiconductors, spinodal decomposition, or secondary phases. In order to clarify this question, we have performed a thorough characterization of the structural and magnetic properties of Co- and Ni-implanted ZnO single crystals. Our measurements reveal that Co or Ni nanocrystals (NCs) are the major contribution of the measured ferromagnetism. Already in the as-implanted samples, Co or Ni NCs have formed and they exhibit superparamagnetic properties. The Co or Ni NCs are crystallographically oriented with respect to the ZnO matrix. Their magnetic properties, e.g., the anisotropy and the superparamagnetic blocking temperature, can be tuned by annealing. We discuss the magnetic anisotropy of Ni NCs embedded in ZnO concerning the strain anisotropy.

13 pages, 14 figures

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Cited by in corpus (15)

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• Structural, Morphological, Optical and Magnetic Property of Mn doped Ferromagnetic ZnO thin film
• Non-DMS related ferromagnetism in transition metal doped zinc oxide
• Ferromagnetic transition metal implanted ZnO: a diluted magnetic semiconductor?
• Formation and annealing of dislocation loops induced by nitrogen implantation of ZnO
• Homogenous and heterogeneous magnetism in (Zn,Co)O
• Controlling exchange bias in Co-CoOx nanoparticles by oxygen content
• Using x-ray diffraction to identify precipitates in transition metal doped semiconductors
• Spinel ferrite nanocrystals embedded inside ZnO: magnetic, electronic and magneto-transport properties
• Hysteresis in the magneto-transport of Manganese-doped Germanium: evidence for carrier-mediated ferromagnetism
• Mid- and far-infrared localized surface plasmon resonances in chalcogen-hyperdoped silicon
• Spin polarized transport current in n-type co-doped ZnO thin films measured by Andreev spectroscopy
• Enhanced magnetic properties in ZnCoAlO caused by exchangecoupling to Co nanoparticles
• Defects-driven magnetism in bulk $\alpha$-Li${}_3$N
• On Using Magnetic and optical methods to determine the size and characteristics of nanoparticles embedded in oxide semiconductors