Absence of ferromagnetism in Co and Mn substituted polycrystalline ZnO

We discuss the properties of semiconducting bulk ZnO when substituted with the magnetic transition metal ions Mn and Co, with substituent fraction ranging from $x=0.02$ to $x=0.15$. The magnetic properties were measured as a function of magnetic field and temperature and we find no evidence for magnetic ordering in these systems down to $T=2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The magnetization can be fit by the sum of a Curie-Weiss term with a Weiss temperature of $\ensuremath{\Theta}⪢100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and a Curie term. We attribute this behavior to contributions from both $t\mathrm{M}$ ions with $t\mathrm{M}$ nearest neighbors and from isolated spins. This particular functional form for the susceptibility is used to explain why no ordering is observed in $t\mathrm{M}$ substituted ZnO samples despite the large values of the Weiss temperature. We also discuss in detail the methods we used to minimize any impurity contributions to the magnetic signal.

[1]  D. A. Schwartz,et al.  Magnetic quantum dots: synthesis, spectroscopy, and magnetism of Co2+ - and Ni2+-doped ZnO nanocrystals. , 2003, Journal of the American Chemical Society.

[2]  Brian R. Bennett,et al.  OBSERVATION OF SPIN INJECTION AT A FERROMAGNET-SEMICONDUCTOR INTERFACE , 1999 .

[3]  A. M. Nazmul,et al.  Ferromagnetism and high Curie temperature in semiconductor heterostructures with Mn δ-doped GaAs and p-type selective doping , 2003 .

[4]  S. Yoon,et al.  Magnetic properties of ZnO-based diluted magnetic semiconductors , 2003 .

[5]  B. Dabrowski,et al.  Structural and magnetic properties of transition metal substituted ZnO , 2004 .

[6]  Jae‐Hyun Kim,et al.  Magnetic properties of epitaxially grown semiconducting Zn1−xCoxO thin films by pulsed laser deposition , 2002 .

[7]  Hiroshi Katayama-Yoshida,et al.  Material Design for Transparent Ferromagnets with ZnO-Based Magnetic Semiconductors , 2000 .

[8]  Search for ferromagnetism in transition-metal-doped piezoelectric ZnO , 2003, cond-mat/0306477.

[9]  Tang,et al.  Magnetoelectronic phenomena at a ferromagnet-semiconductor interface , 2000, Physical review letters.

[10]  Nicola A. Spaldin,et al.  Magnetism in polycrystalline cobalt-substituted zinc oxide , 2003 .

[11]  V.F.Motsnyi,et al.  Electrical spin injection in a ferromagnet/tunnel barrier/semiconductor heterostructure , 2002 .

[12]  Masashi Kawasaki,et al.  Magnetic properties of Mn-doped ZnO , 2001 .

[13]  Masashi Kawasaki,et al.  Room-Temperature Ferromagnetism in Transparent Transition Metal-Doped Titanium Dioxide , 2001, Science.

[14]  E. Rashba.  Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem , 2000, cond-mat/0010473.

[15]  H. Ohno,et al.  Zener model description of ferromagnetism in zinc-blende magnetic semiconductors , 2000, Science.

[16]  Lewicki,et al.  Magnetic susceptibility of semimagnetic semiconductors: The high-temperature regime and the role of superexchange. , 1986, Physical review. B, Condensed matter.

[17]  Robin F. C. Farrow,et al.  Clusters and magnetism in epitaxial Co-doped TiO2 anatase , 2003 .

[18]  Di Wu,et al.  Giant magnetoresistance in organic spin-valves , 2004, Nature.

[19]  V. Ladizhansky,et al.  113CD NMR STUDY OF TRANSFERRED HYPERFINE INTERACTIONS IN THE DILUTE MAGNETIC SEMICONDUCTORS CD1-XCOXS AND CD1-XFEXS AND IMPURITY DISTRIBUTION IN CD0.9 94CO0.006S , 1999 .

[20]  S. Huh,et al.  Anomalous magnetic properties of MnO nanoclusters. , 2002, Journal of the American Chemical Society.

[21]  R. Silver,et al.  Electrical spin injection into semiconductors , 2001 .

[22]  Parmanand Sharma,et al.  Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO , 2003, Nature materials.

[23]  B. Dabrowski,et al.  Origin of Spin-Glass Behavior of Zn1 − xMnxO , 2002, cond-mat/0207349.