Table Of Content6.1.1 Introduction: Scope of the review; Earlier reviews 1
6 Magnetic properties of oxides with
various other structures
6.1 Binary oxides of d trtinsition. elements
6.1.1 Introduction
6.1.1.1 Scopeo f the review
In a 1984 publication in the series (Semiconductors, LB Vol. III/17 g, ch. 9.152) detailed data on the binary
transition metal oxides with emphasis on the transport and optical properties were presented. Therefore, here
only more recent data and the most important earlier data are given, with particular emphasis on the magnetic
properties. For the 3d elements,m uch of the emphasis here is on monoxides since oxides such as Fe,O,, Fe,O,,
Mn,O, etc. are reviewed elsewhere( LBIII/27d, ch. 3.1). Also included here are mixed oxides such as CorNi, -pO,
Co,Mn, -rO and Co,Fe,-,O and diluted oxides such as CopMg,-pO and N$,Mg,-,O, all of which order
magnetically. Magnetic properties of MagnCli phases M,O,, _ i for M = V and Ti are also included. For the 4d
and 5d elements, all the stable binary oxides are included, with emphasis on their magnetic properties, although
none of these oxides order magnetically. Finally, dioxides of the 3d, 4d, and 5d elements, with the rutile or the
distorted rutile structure are grouped together for the purpose of this review.
6.1.1.2 Earlier reviews
Properties of the transition metal oxides have been reviewed in other publications from time to time. These
are listed below.
67 G “Interstitial Alloys” by H.G. Goldschmidt (Butterworths & Co., London, 1967).S eeC hapter 8 on
oxides although some of the data is outdated.
68 A “Insulating and Metallic States in Transition Metal Oxides” by D. Adler, Solid State Phys. 21
(1968) 1.
70 L “Fe Oxides and Fe-Me-O Compounds” by R.A. Lefever in Landolt-Bornstein (Vol. 111/4a),
edited by K.-H. and A.M. Hellwege (Springer-Verlag, 1970).
72 K “Nonstoichiometry, Diffusion and Electrical Conductivity in Binary Metal Oxides” by
P. Kofstad (John Wiley and Sons, 1972).
72 S “Oxide Magnetic Materials” by K.J. Standley (Oxford Univ. Press, 1972).
75 c “Magnetic Oxides, Part I and II”, edited by D.J. Craik (John Wiley and Sons, 1975).
77 B “Electronic Structure of Mott Insulators” by B.H. Brandow, Adv. Phys. 26 (1977) 651.
80 L “Fe Oxides and Fe-Me-O Compounds” by R.A. Lefever in Landolt-Bornstein (Vol. III/lZb,
supplement and extension to Vol. 111/4),e dited by K.-H. and A.M. Hellwege (Springer-Verlag,
1980).
81 T “Non-Stoichiometric Oxides”, edited by 0. Toft Sorensen (Academic Press, 1981).
83 G “IX-VI, Compounds” by A. Goltzene and C. Schwab in Landolt-Bornstein (Vol. 111/17eC, h. 9.3),
edited by 0. Madelung (Springer-Verlag, 1983).
84 D “Basic Properties of Binary Oxides”, edited by A. Dominguez Rodriguez, J. Castaing and
R. Marquez (Univ. of Seville Press, 1984).
84 G “Binary Transition-Metal Oxides” by J.B. Goodenough and A. Hamnett, in Landolt-Bornstein
(Vol. 111/17g,C h. 9.15.2), edited by 0. Madelung (Springer-Verlag, 1984).
Land&-B6rnstein
New Series 111/27g
2 6.1.1 Introduction: List of symbols
6.1.1.3 Symbols and abbreviations
The paramagnetic susceptibility x*) of magnetic materials usually follows the Curie-Weiss law x =
C/(7’- 0). where T is the temperature in K, C is the Curie constant and 0 is the Curie-Weiss temperature
(positive for ferromagnets and negative for antiferromagnets). 0 is determined from the plot of l/x vs. Tin the
limit l/x + 0. Magnetic ordering at the ordering temperature (N&e1t emperature TN for antiferromagnets and the
Curie temperature T, for ferromagnets) is usually accompanied by distortions in the crystal structure due to
exchange-striction effects. Other symbols frequently used are:
a) List of symbols
Symbol Unit Property
a, b, c lattice parameters
a0 lattice parameter of the cubic cell at RT
cln cm3K mol-’ molar Curie constant
c (P) J mol-’ K-r, molar heat capacity (at constant pressure)
cal mol-’ K-r
N rne2, dyn cmp2 elastic stiffness
cij
d g crnT3 density
E, Ea. E, eV, J mol-’ activation energy
E, E, dyn cmm2 Young’s modulus
eV energy band gap
4
mm s-r electric quadrupole splitting
AEQ
structure factor
,’ Hz frequency
9 - spectroscopic splitting factor
H magnetic field (CGS), magnetic field strength (SI)
2 Am-’ magnetic hyperfine field
HbP
Hd Oe spin-flop field
AH Oe EPR linewidth
AH cal mol-’ change in enthalpy at crystal transition
AH, cal mol-’ change in magnetic enthalpy at crystal transition
- (integrated) intensity
I(intl
J eV, cm- l exchange energy (J/k in K)
Kiso - isotropic Knight shift
K x. y. I - Knight shift components
K,, K, -3, erg g-’ anisotropy constant
k F” propagation vector
erg cm-j torque
h/1 - thermal expansion
M G magnetization
An birefringence
P bar, atm, Pa, Torr pressure (hydrostatic)
bar, atm oxygen partial pressure
PO2
Pelf y-1 effective paramagnetic moment
wavevector
i J K-l mol-’ gas constant
S spin quantum number
S VK-’ Seebeckc oefficient (thermoelectric power)
) given in CGS-emu throughout the manuscript
l
6.1.1 Introduction: List of symbols 3
Symbol Unit Property
T “C,K temperature
K ferro- or ferrimagnetic Curie temperature
Tc
K superconducting transition temperature
TC
K melting temperature
TM
“C,K Ntel temperature
TN
K magnetic transition temperature (due to spin reorientation, see
TW
subsect. 6.1.2.1,C uO)
T K short range magnetic transition temperature
SR
“C,K (metal-insulator) transition temperature
r,
V A3 volume of unit cell
Hz components of the electric field gradient
vii
mm s-l velocity of absorber in Miissbauer effect (sometimes used for
V
sound velocity)
bar stress
- number of molecules per unit cell
dB cm-’ ultrasonic attenuation coefficient
-1 absorption coefficient
Fl linear thermal expansion coefficient
angle between a and c axis in R structure
deg
mm s-l isomer shift
- magnetic loss factor
- dielectric constant
- real, imaginary part of dielectric constant
- asymmetry parameter of electric quadrupole splitting
K Curie-Weiss temperature
K Debye temperature
deg, rad angle
nm wavelength
- (saturation) magnetostriction constant
J T-‘(erg G-l) Bohr magneton
-1 wavenumber
iit electric quadrupole frequency
ncm, Qrn resistivity
g-J-lcm-1, Q-lm-l electrical conductivity
- order parameter (see Figs. 25, 26)
G cm3 g-l, magnetic moment per unit mass ( = specific magnetization)
A mz kg-’
G cm3mol-’ magnetic moment per mole ( = molar magnetization)
cm3 g-l specific magnetic susceptibility (CGS-emu)
cm3 mol-’ molar magnetic susceptibility (CGS-emu)
- temperature-independent van Vleck susceptibility
angular frequency
s-1
eV photon energy
Landok-Bibstein
New Series 111/27g
4 6.1.2.1 Simple monoxides MO [Ref. p. 26
b) List of abbreviations
dc direct current
exp experimental
EFG electric field gradient
fc, FC field cooling
int integrated
IS isomer shift
I, liq liquid
LNT liquid nitrogen temperature
m monoclinic
Mi Rutile-type phases
NMR, nmr nuclear magnetic resonance
OD optical density
quadrupole shift
if rutile (structure)
rel relative
rh rhombohedral
RT room temperature
tetr tetragonal
tot total
wiistite
ZFC zero-field cooling
1, II perpendicular, parallel (to a crystallographic axis)
6.1.2 Monoxides of 3d transition elements
6.1.2.1 Simple monoxidesM O
General remarks [70R], [58R], [SIS]
Of the nine 3d transition elements viz. SC,T i, V, Cr, Mn, Fe, Co, Ni and Cu, only SCa nd Cr do not seemt o
form stable monoxides, viz. ScO and CrO. TiO, VO, MnO, FeO, Co0 and NiO crystallize in the NaCl structure
(Fig. l), whereas CuO has a monoclinic structure, probably because Cu*+ exhibits a Jahn-Teller distortion.
Properties of all the oxides are sensitivet o deviations from oxygen stoichiometry. TiO is a metallic conductor and
a superconductor, VO is a semimetal and MnO, FeO, COO, NiO, CuO are weak semiconductors and they order
antiferromagnetically below their respective Ntel temperatures TN.
Fig. 1. The NaCl structure in which TiO, VO, MnO, Fe0
COO,a nd NiO crystallizeL. ight spheresa re metala tomsa nd
dark spheresa re oxygena toms.
Landoh-Bbstcin
New Series 11127g
4 6.1.2.1 Simple monoxides MO [Ref. p. 26
b) List of abbreviations
dc direct current
exp experimental
EFG electric field gradient
fc, FC field cooling
int integrated
IS isomer shift
I, liq liquid
LNT liquid nitrogen temperature
m monoclinic
Mi Rutile-type phases
NMR, nmr nuclear magnetic resonance
OD optical density
quadrupole shift
if rutile (structure)
rel relative
rh rhombohedral
RT room temperature
tetr tetragonal
tot total
wiistite
ZFC zero-field cooling
1, II perpendicular, parallel (to a crystallographic axis)
6.1.2 Monoxides of 3d transition elements
6.1.2.1 Simple monoxidesM O
General remarks [70R], [58R], [SIS]
Of the nine 3d transition elements viz. SC,T i, V, Cr, Mn, Fe, Co, Ni and Cu, only SCa nd Cr do not seemt o
form stable monoxides, viz. ScO and CrO. TiO, VO, MnO, FeO, Co0 and NiO crystallize in the NaCl structure
(Fig. l), whereas CuO has a monoclinic structure, probably because Cu*+ exhibits a Jahn-Teller distortion.
Properties of all the oxides are sensitivet o deviations from oxygen stoichiometry. TiO is a metallic conductor and
a superconductor, VO is a semimetal and MnO, FeO, COO, NiO, CuO are weak semiconductors and they order
antiferromagnetically below their respective Ntel temperatures TN.
Fig. 1. The NaCl structure in which TiO, VO, MnO, Fe0
COO,a nd NiO crystallizeL. ight spheresa re metala tomsa nd
dark spheresa re oxygena toms.
Landoh-Bbstcin
New Series 11127g
Ref. p. 261 6.1.2.1 Simple monoxides MO 5
General properties [84D], [SSR], [SlS], [60Rl], [60R2]
Whereas Fig. 1 depicts the NaCl crystal structure of TiO, VO, MnO, FeO, Co0 and NiO, the magnetic unit
cell and arrangement of magnetic moments in MnO, FeO, Co0 and NiO below their respective Ntel
temperatures are given in Fig. 2. Table 1 summarizes some of the important crystallographic and magnetic data
for the oxides. In Fig. 3, the stable binary oxides of the 3d series as a function of oxygen pressure are noted (not
included in this diagram are the Magnkli phaseso f the Ti-0 and V-O systems).I n Fig. 4, the data on the melting
temperature TM and lattice constant a, for the oxides with the NaCl structure are plotted. The melting
temperature is minimum for FeO, whereas the lattice constant jumps from VO to MnO, presumably due to
magnetic ordering in the latter. From MnO to NiO, the lattice constant decreasesw hereas TN increases( Table 1).
Table 1. Crystallographic, magnetic and electrical properties of the 3d monoxides with the NaCl structure.
For referencess ee [84D] and text in section 6.1.2.1.
d” Oxide %C~I Wcm31 TME l *Spin-order TN [K] PW cm1
at 300K
TvoiO 44..0178 45..9438 '22002633 1100--43
MFen,O,,, 0 44..4340 55..74 4 21065481 AAFF 119188 1100’-z5
cNoiOo 44..2167 66..4657 22205778 AAFF 258293 1100’’03
cue monoclinic 6.515 1599 AF 230, 213 (T,,) 1010
tl
MnO I
I
I I I
.JL
Fig. 2. Magnetic unit cell of MnO, FeO, Co0 and NiO I I I- iwo-phase ‘region 1
[58 R] and [Sl S]. Positive and negative signs refer to oppos- ---- single-phase-region
itely directed moments on the cations, and oxygen ions are I I
omitted from the diagram since they carry no magnetic 0.5 1.0 1.5 2.0 2.5
moment. The easy direction of moment alignment is along Oxygen to metal ratio 1x1
{ 1 12) directions in MnO and NiO, along [l 1 l] direction in
Fe0 and at an angle of 27.4” from [0 0 l] in the (1 10) planes Fig. 3. Oxygen pressure-composition phase diagram for 3d
for COO. [57 K, 60 Rl, 60 R2,60 S, 66 B, 78 H]. oxides [70 R].
Land&-B&stein
New Series III/27g
6 6.1.2.1 Simple monoxides MO [Ref. p. 26
3.9
TiO VO MnO Fe0 coo NiO
Fig. 4. The lattice constant a, and melting temperature TMf or
oxides with the NaCl structure. Based on the data from
[84 D].
TiO
TiO, can bc prepared for 0.70 < x < 1.30 in the NaCl structure (Fig. 5 and [64D], [66D], [70B] and [750]).
Fig. 6 gives variation of a, and d with x and Fig. 7 the electrical resistivity p vs. l/Tfor several x. TiO, becomes
superconducting near 1 K (Fig. 8 and Fig. 9). For x = 1, TiO is a Pauli paramagnet with xe = 1.7. low6 cm3/g,
with no temperature dependenceu p to 1000 K [66D]. For x 4 1,x decreasesa s Tdecreases,p robably becauseo f
trapped carriers at unfilled bonds. Larger deviations from x = 1 produce ordering of vacancies,[ 67W], [7OW],
[79T], [SlC], [81M] and an effective monoclinic structure.
2200
'C
2000
11880000
1600
11LLOOOO
II
6.
Y200
11000000
880000
600
400
00 00..22 00..44 00..66 00..88 11..00 11..22 1.4 1.6
Fig. 5. The Ti-0 phase diagram [84G]. See also [70B]. a and 0 refer to the
hexagonal and cubic form of Ti metal and TiO (low) is monoclinic whereas TiO
(high) is cubic.
Landolt-B6mstein
New Series 111/27g
Ref. p. 261 6.1.2.1 Simple monoxides MO 7
5.2 66dd I
Q8ccmm TiOx
g/cm3 I I x= 1.17I
5.0 44
t
-m
33
4.8
4.20
t
a
22
4.19 I
aa--
I 438
11OO--44
B 99
ee
4.lY
77
66
n0 22 44 66 88 1100
4.l6
0.7 0.8 0.9 1.0 1.1 1.2 1.3 ll//ll--
Fig. 7. TiO,. Resistivity p vs. reciprocal temperature for five
compositions [70 B]. See also [69 L].
Fig. 6. TiO,. Lattice parameter a, and measuredd ensity d vs.
x for TiO,. Different symbols represent data from different
sources. The solid lines are least-squares fits for all data
[70B].
2.5 I
K TiOx
‘:lh;i
00..9900 00..9955 11..0000 11..0055 11..1100 11..1155 11..2200 11..2255
x-
Fig. 8. TiO,. Superconducting transition temperature T, vs. x 11
[70 B]. Full circles: data from [65 H] and the remaining data
are from [70 B]. See also[72 R2]. 0.2 0.5 0.8 1.1 1.4 K 1.7
T-
Fig. 9. TiO,. Heat capacity C of three samplesi n zero magnetic
field, plotted as C/T vs. T. The peaks are due to superconduct-
ing transitions and solid lines representt he heat capacity in the
normal state [75 01.
Landolt-BBmstein
New Series III/27g
8 6.1.2.1 Simple monoxides MO [Ref. p. 26
vo
Like TiO,, VO, is also stable for large range of x (Fig. 10) [70B]. However, as a, increasesw ith x, the density d
decreases,a more normal behavior (Fig. 10). The molar magnetic susceptibility x,,, vs. T for several x values is
shown in Fig. 11 and Fig. 12. x,,, increasesa s Tdecreases,p resumably becauseo f paramagnetic defects.H owever,
I,,, does not follow the Curie-Weiss law and there is no magnetic ordering (Fig. 12).T he behavior of x vs. T does
not appear to be well understood. Heat capacity is shown in Fig. 13.
10
g/cm3 cm3/mol
5.7 8
5.5
I
t,
4.15
A
4.10
0
I 0.8 0.9 1.0 1.1 1.2 1.3
Co5
Fig. 11. VO,. Molar susceptibility x,,, vs. x at various temper-
4.00 atures [70 B].
a7 0.8 0.9 1.0 1.1 1.2 1.3 1.1,
x-
Fig. 10. VO,. Lattice parameter ~7,a nd measured density d
vs. x. Full symbols are for single crystals. The solid line is a
least squares fit to the density data [70 B].
0 50 100 150 200 250 K 300
Fig. 12. VO,. Inverse of the molar susceptibility xrn measured
at 9.84 kOe vs. temperature for nine compositions [70B].
land&-B6mstein
New Series 111:?7g
Ref. p. 261 6.1.2.1 Simple monoxides MO 9
MnO
Mn, -XO is generally metal deficient (x < 0.1). The crystal structure is NaCl till TN N 118 K (Fig. 13) [51T]
below which a trigonal distortion occurs (Fig. 14) [70M]. For large x, crystallization of Mn,O, as an impurity is
observed (Fig. 15 and Fig. 16) [SlJl] and [82Sl]. Well above TN, short range magnetic order is evident from
EPR (Fig. 17) [83N] and spin-polarized photoelectron diffraction (Fig. 18) [89H]. The ,optical absorption
spectra shows three prominent bands in the visible range (Fig. 19), which are blue-shifted below TN (Fig. 20)
[83Sl]. At TN, distinct anomalies are observed in elastic constants (Figs. 21 and 22) [82S2] and [SOP], thermal
expansion (Fig. 23) [73B], dielectric constant (Fig. 24) [SlSl], magnetic order parameter (Figs. 25 and 26) [SOB]
and [81Sl], and magnetic susceptibility (Fig. 27) [81J2]. Seea lso Fig. 64. Below TN,d omains are present (Fig. 27)
and anisotropy in the (111) plane is much smaller than the out-of-plane anisotropy (Fig. 28) [67B]. The nearest-
neighbor and next-nearest-neighbor exchange constants, J,/k and J,/k, are 10 K and 11K respectively [88S2].
Low-temperature magnetic moment is 2.34 pa/MnZf [73J]. For spin-wave dispersion see [74P].
r
4.ut6
MnO
A
87.2
87.0
160 2LO K 320
T-
Fig. 14. MnO. Lattice constant a and unit cell volume V
between 7 and 300 K [70 M]. The solid line includes a
contribution from magnetic correlation whereas the broken
0 50 100 150 200 250 K 300 line IS the predicted curve for a Debye solid. Below I&, the
dashed line through the experimental points includes calcu-
lations for trigonal distortion [65 L].
Fig. 13. Heat capacities of Fe,,,,,O, MnO and VO [51 T].
See also [28 M].
Fig. 15. MnO. Magnetic susceptibility of unannealed and
annealed samples [Sl J 11. The anomaly in the unannealed
sample is due to Mn,O, impurity [SOJ ], seea lso [59 M] and
[84 H].
T-
Land&-BBmstein
New Series III/27g
