Pure ultrafine ZnFe2O4 particles have been obtained from mechanosynthesis of the ZnO and Fe2O3 oxides. The average grain diameter was estimated from x-ray diffraction to be 〈d〉=36(6) nm. Refinement of neutron diffraction data showed that the resulting cubic spinel structure is oxygen deficient, with ∼7% of Fe3+ ions occupying the tetrahedral A sites. Magnetization curves taken at 4.2 K showed the absence of saturation in fields up to H=9 T, associated with a spin-canting produced by the milling process. Field-cooled (FC) and zero-field cooled (ZFC) curves showed irreversible behavior extending well above room temperature, which is associated with spin disorder. Annealing samples at 300 °C yields an average grain size 〈d〉=50(6) nm, and ∼16% of Fe3+ ions at A sites. Partial oxygen recovery is also deduced from neutron data refinement in annealed samples. Concurrently, decrease of magnetic irreversibility is noticed, and assigned to partial recovery of the collinear spin structure. Complex Mössbauer spectra were observed at room temperature and 80 K, with broad hyperfine field distributions spanning from ∼10 to ∼40 T. At T=4.2 K, hyperfine field distributions indicate high disorder in Fe local environments. The above data suggest the existence of Fe-rich clusters, yielding strong superexchange interactions between Fe ions at A and B sites of the spinel structure.

1.
L. J.
de Jongh
,
Appl. Organomet. Chem.
12
,
393
(
1998
).
2.
R. H.
Kodama
and
A. E.
Berkowitz
,
Phys. Rev. B
59
,
6321
(
1999
).
3.
S. Krûpica and P. Novak, “Oxide spinels,” in Ferromagnetic Materials, edited by E. P. Wolfarth (North-Holland, Dordrecht, 1982), Vol. 3.
4.
W.
Schiessl
et al.,
Phys. Rev. B
53
,
9143
(
1996
).
5.
J. M.
Hastings
and
L. M.
Corliss
,
Rev. Mod. Phys.
25
,
114
(
1953
).
6.
J. C.
Ho
,
H. H.
Hamdeth
,
Y. Y.
Chen
,
S. H.
Lin
,
Y. D.
Yao
,
R. J.
Willey
, and
S. A.
Oliver
,
Phys. Rev. B
52
,
10122
(
1995
).
7.
Y. G.
Chukakin
and
V. R.
Shirts
,
Sov. Phys. Solid State
30
,
1683
(
1988
).
8.
U.
König
,
E. F.
Bertaut
,
Y.
Gros
,
M.
Mitrikov
, and
G.
Chol
,
Solid State Commun.
8
,
759
(
1970
).
9.
J. M. D.
Coey
,
Phys. Rev. Lett.
27
,
1140
(
1971
).
10.
A. H.
Morrish
and
K.
Haneda
,
J. Magn. Magn. Mater.
35
,
105
(
1983
).
11.
B.
Martinez
,
X.
Obradors
,
L.
Balcells
,
A.
Rouanet
, and
C.
Monty
,
Phys. Rev. Lett.
80
,
181
(
1998
).
12.
G. F.
Goya
,
H. R.
Rechenberg
, and
J.
Jiang
,
J. Appl. Phys.
84
,
1101
(
1998
).
13.
M.
Yokoyama
,
E.
Otha
,
T.
Sato
,
T.
Komaba
, and
T.
Sato
,
J. Phys. IV
7
,
C1
-
521
(
1997
).
This content is only available via PDF.
You do not currently have access to this content.