The role of iron doping on magnetic properties of hydrothermal anatase TiO2:57Fe (0–1 at. %) nanoparticles is investigated by combining superconducting quantum interference device magnetometry with Mössbauer and electron paramagnetic resonance techniques. The results on both as-prepared and thermally treated samples in reduced air atmosphere reveal complexity of magnetic interactions, in connection to certain iron ion electron configurations and defects (oxygen vacancies, F-center, and Ti3+ ions). The distribution of iron ions is predominantly at nanoparticle surface layers. Formation of weak ferromagnetic domains up to 380 K is mainly related to defects, supporting the bound magnetic polaron model.

1.
T.
Dietl
,
H.
Ohno
,
F.
Matsukura
,
J.
Cibert
, and
D.
Ferrand
,
Science
287
,
1019
(
2000
);
[PubMed]
2.
M.
Venkatesan
,
C. B.
Fitzgerald
, and
J. M. D.
Coey
,
Nature
420
,
630
(
2005
);
T.
Fukumura
,
Y.
Yamadaa
,
H.
Toyosakia
,
T.
Hasegawab
,
H.
Koinuma
, and
M.
Kawasakia
,
Appl. Surf. Sci.
223
,
62
(
2004
).
3.
S. A.
Wolf
,
D. D.
Awschalom
,
R. A.
Buhrman
,
J. M.
Daughton
,
S.
von Molnar
,
M. L.
Roukes
,
A. Y.
Chtchelkanov
, and
D. M.
Treger
,
Science
294
,
1488
(
2001
);
[PubMed]
4.
S. A.
Chambers
and
R. F. C.
Farrow
,
MRS Bull.
28
,
729
(
2003
);
S. A.
Chambers
,
S. M.
Heald
, and
T.
Droubay
,
Phys. Rev. B
67
,
100401(R)
(
2003
);
S. A.
Chambers
,
T.
Drouby
,
C. M.
Wang
,
A. S.
Lea
,
R. F. C.
Farrow
,
L.
Folks
,
V.
Deline
, and
S.
Anders
,
Appl. Phys. Lett.
82
,
1257
(
2003
).
5.
J. D.
Bryan
and
D. R.
Gamelin
,
Prog. Inorg. Chem.
54
,
47
(
2005
);
J. D.
Bryan
,
S. M.
Heald
,
S. A.
Chambers
, and
D. R.
Gamelin
,
J. Am. Chem. Soc.
126
,
11640
(
2004
);
[PubMed]
J. D.
Bryan
,
S. A.
Santangelo
,
S. C.
Keveren
, and
D. R.
Gamelin
,
J. Am. Chem. Soc.
127
,
15568
(
2005
).
[PubMed]
6.
Z. Q.
Zhao
,
B. K.
Tay
,
J. S.
Chen
,
J. F.
Hu
,
B. c.
Lim
, and
G. P.
Li
,
Appl. Phys. Lett.
90
,
152502
(
2007
);
S. M.
Gupta
and
M.
Tripathi
,
Chin. Sci. Bull.
56
,
1639
(
2011
).
7.
A. M.
Calle
,
L. C.
Sanchez
,
J. D.
Rboleda
,
J. J.
Beltran
,
C. A.
Barrero
,
J.
Osorio
, and
K.
Nomura
,
Microelectron. J.
39
,
1322
(
2008
).
8.
Y.
Matsumoto
,
M.
Murakami
,
T.
Shono
,
T.
Hasegawa
,
T.
Fukumura
,
M.
Kawasaki
,
P.
Ahmet
,
T.
Chikyow
,
S.
Koshihara
, and
H.
Koinuma
,
Science
291
,
854
(
2001
).
9.
N.
Hong
,
W.
Prellier
,
J.
Sakai
, and
A.
Hassini
,
Appl. Phys. Lett.
84
,
2850
(
2004
);
N.
Hong
,
J.
Sakai
,
W.
Prellier
,
A.
Hassini
,
A.
Ruyter
, and
F.
Gervais
,
Phys. Rev. B
70
,
195204
(
2004
);
N.
Hong
,
N.
Poirot
, and
J.
Sakai
,
Appl. Phys. Lett.
89
,
042503
(
2006
);
N.
Hong
,
J.
Sakai
,
N.
Poirot
, and
V.
Brize
,
Phys. Rev. B
73
,
132404
(
2006
).
10.
J.
Chen
,
P.
Rulis
,
L. Z.
Ouyang
,
S.
Satpathy
, and
W. Y.
Ching
,
Phys. Rev. B
74
,
235207
(
2006
).
11.
J. M. D.
Coey
,
A. P.
Douvalis
,
C. B.
Fitzgerald
, and
M.
Venkatesan
,
Appl. Phys. Lett.
84
,
1332
(
2004
);
J. M. D.
Coey
,
M.
Venkatesan
, and
C. B.
Fitzgerald
,
Nat. Mater.
4
,
173
(
2005
);
[PubMed]
J. M. D.
Coey
,
Curr. Opin. Solid State Mater. Sci.
10
,
83
(
2006
) and references therein;
J. M. D.
Coey
,
K.
Wongsaprom
,
J.
Alaria
, and
M.
Venkatesan
,
J. Phys. D: Appl. Phys.
41
,
134012
(
2008
).
12.
Z.
Wang
,
W.
Wang
,
J.
Tang
,
L. D.
Tung
,
L.
Spinu
, and
W.
Zhou
,
Appl. Phys. Lett.
83
,
518
(
2003
);
Z. J.
Wang
,
J. K.
Tang
,
Y. X.
Chen
,
L.
Spinu
,
W.
Zhou
, and
L. D.
Tung
,
J. Appl. Phys.
95
,
7384
(
2004
).
13.
B.
Choudhury
and
A.
Choudhury
,
Mater. Sci. Eng., B
178
,
794
(
2013
).
14.
J.
Xu
,
S.
Shi
,
L.
Li
,
X.
Zhang
,
Y.
Wang
,
X.
Chen
,
J.
Wang
,
L.
Lv
,
F.
Zhang
, and
W.
Zhong
,
J. Appl. Phys.
107
,
053910
(
2010
);
X.
,
J.
Li
,
X.
Mou
,
J.
Wu
,
S.
Ding
,
F.
Huang
,
Y.
Wang
, and
F.
Xu
,
J. Alloys Compd.
499
,
160
(
2010
).
15.
A. K.
Rumaiz
,
B.
Ali
,
A.
Ceylan
,
M.
Boggs
, and
S. I.
Shah
,
Solid State Commun.
144
,
334
(
2007
).
16.
M. N.
Grecu
,
S.
Constantinescu
,
D.
Tarabasanu-Mihaila
,
D.
Ghica
, and
I.
Bibicu
,
Phys. Status Solidi B
248
,
2927
(
2011
).
17.
M. N.
Grecu
,
D.
Macovei
,
D.
Ghica
,
C.
Logofatu
,
S.
Valsan
,
N. G.
Apostol
,
G. A.
Lungu
,
R. F.
Negrea
, and
R. R.
Piticescu
,
Appl. Phys. Lett.
102
,
161909
(
2013
).
18.
J. Y.
Kim
,
J. H.
Park
,
B. G.
Park
,
H. J.
Noh
,
S. J.
Oh
,
J. S.
Yang
,
D. H.
Kim
,
S. D.
Bu
,
T. W.
Noh
,
H. J.
Lin
,
H. H.
Hsieh
, and
C. T.
Chen
,
Phys. Rev. Lett.
90
,
017401
(
2003
).
19.
L. C.
Pereira
,
M. R.
Nunes
,
O. C.
Monteira
, and
A. J.
Silvestre
,
Appl. Phys. Lett.
93
,
222502
(
2008
).
20.
T. C.
Kaspar
,
T.
Droubay
,
S. M.
Heald
,
M. H.
Egelhard
,
P.
Nichimuthu
, and
S. A.
Chambers
,
Phys. Rev. B
77
,
201003(R)
(
2008
);
L. C.
Nistor
,
C.
Ghica
,
V.
Kuncser
,
D.
Pantelica
,
J.-J.
Grob
,
G.
Epurescu
, and
M.
Dinescu
,
J. Phys. D: Appl. Phys.
46
,
065003
(
2013
).
21.
B. K.
Rao
and
P.
Jena
,
Phys. Rev. Lett.
89
,
185504
(
2002
).
22.
P. A.
Wolff
,
R. N.
Bhatt
, and
A. C.
Durst
,
J. Appl. Phys.
79
,
5196
(
1996
);
A. C.
Durst
,
R. N.
Bhatt
, and
P. A.
Wolff
,
Phys. Rev. B
65
,
235205
(
2002
).
23.
J. M. D.
Coey
,
J. Appl. Phys.
97
,
10D313
(
2005
);
Z.
Ren
,
G.
Xu
,
X.
Wei
,
Y.
Liu
,
X.
Hou
,
P.
Du
,
W.
Weng
,
G.
Shen
, and
G.
Han
,
Appl. Phys. Lett.
91
,
063106
(
2007
).
24.
See supplementary material http://dx.doi.org/10.1063/1.4917037 for Table IS for XRD data of TiO2 samples as prepared (AP) and thermally treated (TT); Table IIS for hyperfine parameters of AP and TT samples S1 and S2; Fig. 1S for the room temperature magnetization curves M(H) of the ferromagnetic part, fitted with a BMP model; and Figs. 2S and 3S for X-band EPR spectra of paramagnetic defects in S0T, S1T, S2T, and S1 treated in air, 2 h at 650 °C, respectively.
25.

Starting from the assumption that the BMP is not strictly related to the presence of Fe related magnetic moments but to other kind of local magnetic moment carrier (e.g., associated to oxygen vacations or other defects), we have proceed to an estimation within the BMP model of sample S0 as well as for Fe doped samples. Because the magnetic ordering at low temperature might involve also clusters in the magnetic blocked regime, we have estimated M (H) saturation at 380 K where only magnetic entities responsible for RTFM contribute to the magnetism. The number of magnetic carriers per gram is 1018, both in S1 and S0 samples. Therefore, the Fe ions are not important in RTFM at low concentration of iron, so the polaron should be assigned to other defects.

26.
M.
Knobel
,
W. C.
Nunes
,
L. M.
Socolovsky
,
E.
De Biasi
,
J. M.
Vargas
, and
J. C.
Denardin
,
J. Nanosci. Nanotechnol.
8
,
2836
(
2008
).
27.
M. D.
Stiles
and
R. D.
McMichael
,
Phys. Rev. B
60
,
12950
(
1999
).
28.
H.
Min Lee
,
J. Magn. Magn. Mater.
310
,
2099
(
2007
).
29.
A.
Bandyopadhyay
,
S.
Sutradhar
,
B. J.
Sarkar
,
A. K.
Deb
, and
P. K.
Chakrabarti
,
Appl. Phys. Lett.
100
,
252411
(
2012
).
30.
C.
Chiorescu
and
J. L.
Cohn
,
Phys. Rev. B
76
,
020404(R)
(
2007
).
31.
S. K. S.
Patel
,
S.
Kurian
, and
N. S.
Gajbhiye
,
Mater. Res. Bull.
48
,
655
(
2013
).
32.
V.
Kuncser
,
G.
Schinteie
,
B.
Sahoo
,
W.
Keune
,
D.
Bica
, and
L.
Vekas
,
J. Phys.: Condens. Matter
19
,
016205
(
2007
).
33.
L. A.
Errico
and
M.
Rentería
,
Phys. Rev. B
72
,
184425
(
2005
).
34.
C. E.
Rodrigues-Torres
,
J. Phys.: Condens. Matter
20
,
135210
(
2008
).
35.
M.
Grätzel
and
R. F.
Howe
,
J. Phys. Chem
94
,
2566
(
1990
).
36.

The spin concentration of EPR centers was determined on the ELEXSYS E580 Bruker spectrometer, equipped with the Super High QE (SHQE) cavity resonator (ER 4123SHQE), by using the absolute spin quantitation resonator calibration routine, included in the XEPR software from Bruker, based on the double integration of the corresponding spectra.

37.
G.
Pecchini
,
P.
Reyes
,
T.
Lopez
,
R.
Gomez
,
A.
Moreno
,
J. L. G.
Fierro
, and
A.
Martinez Arias
,
J. Sol-Gel. Sci. Technol.
27
,
205
(
2003
).
38.
A.
Shengelaya
,
G. M.
Zhao
,
H.
Keller
, and
K. A.
Muller
,
Phys. Rev. B
61
,
5888
(
2000
).
39.
D.
Pan
,
G.
Xu
,
L.
Lv
,
Y.
Yong
,
X.
Wang
,
J.
Wan
, and
G.
Wang
,
Appl. Phys. Lett.
89
,
082510
(
2006
).
40.
Y.
Sun
,
T.
Egawa
,
C.
Shao
,
L.
Zhang
, and
X.
Yao
,
J. Phys. Chem. Solids
65
,
1793
(
2004
).

Supplementary Material

You do not currently have access to this content.