- Email: [email protected]
Transport properties of Nd7Ni3
Journal of Magnetism and Magnetic Materials 177-181 (1998) 1117-1118
Journalof magnetism and magnetic materials
,~l
ELSEVIER
Transport properties of NdTNi3 H. K a d o m a t s u a'*, Y. Itoh b, H. F u k u d a ~, T. T s u t a o k a ~, T. T o k u n a g a ~ Cryogenic Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739, Japan bFacult~' of Liberal Arts Fukuyama University, Fukuyama 729-02, Japan FaculO, of School Education, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739, Japan
Abstract Electrical resistivity of Nd~Ni3 shows anomalies at the N6eI temperature TN = 29 K and the Curie temperature Tc = 14 K but does not show any change at the spin reorientation temperature Ta = 8.7 K. The thermoelectric power has also broad humps around 250 and 50 K as well as a sharp break at TN and a minimum at 10 K. The corresponding Hall coefficient shows anomalies at TN, Tc and TR, following the Curie-Weiss-Iaw-like behavior above TN. ~/ 1998 Elsevier Science B.V. All rights reserved.
Keywords: Transport properties; Thermoelectric power; Hall effect; Electrical resistivity - temperature dependence
In N d ; N i 3 the successive magnetic-phase transitions and metamagnetic transitions were found by magnetic studies [-ll. Together with the preliminary neutron diffraction study [2], it is expected that below TN = 29 K magnetic moment is in the c-plane, the magnetic periodicity is about three times lattice c, and the magnetic structure below Tc = 14 K is conical or canted. In 4f compounds conduction bands play an important role in the magnetic properties. Therefore the electrical resistivity p, thermoelectric power S and Hall coefficient Ru were investigated in this work. Fig. 1 shows p of NdvNis as a function of temperature T. The inset shows the R(T) curve up to 300 K. At TN and Tc remarkable and slight breaks appear. On the other hand, at the spin reorientation temperature TR = 8.7 K no anomaly is found. Above TN the temperature dependence of p shows a concave-downward curvature. In Fig. 2 is shown S of an isoelectronic compound LaTNis as a function of T in order to estimate the non-magnetic contribution to S in Nd~Nis. It is assumed that the S curve has two contributions, namely, a phonon drag term Sph and a non-magnetic Mott's diffusion term SnmE3], as schematically shown by dotted lines in Fig. 2. According to Burkov et al.'s model [4], the non-linear temperature dependence OfSnm indicates that Fermi level locates at the steep upward-slope in the density of states. *Corresponding author. Tel.: +81 824 24 6276; fax: + 81 824 24 0746; e-mail: [email protected].
TN
4o
NdTNi3
~ /.
-"
f--
og "~
.' 20
Tc
200
,
L ,
b ,
I
~0
TR . v~././/" •
07 T(K~
i
2~0
r
4r0
T(~ Fig. 1. Electrical resistivity p of NdvNi3 as a function of temperature T. The inset shows the p versus T curve up to 300 K.
kaTNi3
~2 . . . - ' o f "~'~- S ~
-~
1;0
T(K)
2;0
~oo
Fig. 2. Thermoelectric power S of LavNis as a function of temperature T. Some components to S are shown by dotted curves. For details see the text.
0304-8853/98/$19.00 £i,: 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 8 8 5 3 ( 9 7 ) 0 0 5 6 2 - 3
H. Kadomatsu et aL / Jom'nal of Magnetism and Magnetic Materials 177-181 (1998) tlt7-1118
1118
In Fig. 3 is shown S of NdvNi3 as a function of T. The inset shows S(T) up to 50 K. The S(T) curve shows broad humps around 250 and 50 K, a sharp break at TN and a minimum at 10 K. This S(T) curve can be decomposed into a magnetic term Sma~, a phonon drag term Sph, crystal-field effect term S~y and a MoWs diffusion term S,m, as schematically shown by dotted lines in Fig. 3. Fulde and Peschel [5] calculated S by taking account of crystal-field levels and found that So~yhas a peak near T = 0.35/k~ where ~5is crystal-field splitting energy and kB the Boltzmann constant. Unfortunately, we have no available data concerning the crystal field except for Ce~Nis [6]. The term shown by S#, + S~,y in Fig. 3 spreads over in a wider temperature range than Spt, of LaTNi3 (Fig. 2). The contribution of S m, may most likely overlap with Sp> AbeFskii and Irhkin [71 calculated S on the basis of the model that magnetic periodicity in antiferromagnetic ordering produces a magnetic Brillouin zone and an energy gap produced by this zone deforms the conduction band near the Fermi level. We followed their calculation but the result was different from the one obtained by them and it is as follows: +
Sm~g = + 3--57-~-~ t \(A - 1 ) 2
1- t + C
AC3:2
) ,
(1)
+2,,/1--t +B(1--t +C) where
t = T/TN,
A =I/kr,
(,,,kor~ )
= \ 2h2l
u~+ = +_(l-kv),
/,,kor~ k "~
'
c = \ -5p7-
V'
kF is Fermi wave vector and 1 is a magnetic wave vector. The meaning of the other symbols is given in Ref. ]-7]. However, Eq. (1) is qualitatively in agreement with one
6
~
L
NdzNi3
L'
=oL ~
T.
'
4
~ ~o r 20 T(~
"""
100
T(K)
200
40
300
Fig. 4. Hail coetScient RH of NdTNi3 as a function of temperature T. The inset shows RH{T) below 50 K.
obtained by Abel'skii and Irhkin. From the concaveupward curvature of the S(T) curve below TN, it is deduced that the conduction carrier has a hole-like character as a result of the appearance of magnetic Brillouin zone below TN. As seen from the inset, the effects of magnetic-phase transitions at Tt< and Tc to S modify Abel'skii and Irhkin's simple pictures. In Fig. 4 are shown the Hall coefficient RH of NdTNis as a function of T. Anomalies appear at TN, Tc and Try. The temperature dependence follows the Curie-Weiss law above TN. With a semi-empirical equation, the Hall coeiticient is written as RH = Ro + Re%, where Ro, RE and 7, are ordinary, extraordinary Hall coefficients and magnetic susceptibility, respectively. The value of R0 is estimated to be zero. However, RH of the isoelectronic LaTNi3, which is not described in this paper, is positive in sign in the temperature range 4.2K ~< T ~< 300 K and does not contradict the S result (hole character of conduction electron). In conclusion, in Nd,TNi3, the magnetic states are reflected considerably transport quantities p, S and RH. For obtaining the anisotropic information, experiments on the single crystal should be done.
References Nd7Ni3
E
3C
i
4
;
i
/
~
7 / / ".,, Sp +S~:,,z
TN
e2
Tel
[t] T. Tsutaoka, H. Fukuda, T. Tokunaga, H. Kadomatsu, Y. Itoh, J. Magn. Magn. Mater. 167 (1997) 248. [2] S. Kawano, Y. Ando, M. Kurisu, private communication. [3] F.J. Blatt, P.A. Schroeder, C.L. Foiles, D. Greig, Thermoelectric Power of Metals, Plenum Press, New York, 1976.
/S
m
/l~'°l
'~
0 I
100
,
T(K)
i b ~ ,
20
I
200
[ ,/
40 T(k3
300
Fig. 3. Thermoelectric power S of NdTNi3 as a function of temperature T. Some components to S are shown by dotted curves. For details see the text. The inset shows S(T) below 50 K.
[4] A.T. Burkov, E. Gratz, E. Bauer, R. Ressel, J. Alloys and Compounds 198 (1993) 1177. [5] P. Fulde, I. Peschel, Adv. Phys. 21 (1972) 1. [6] J.G. Sereni, O. Trovarelli, J.P. Kappler, C. Paschke, T. Trappmann, H. v. L6hneysen, Physics B 199&200 (1994) 567. [7] S.S. Abel'skii, Y.P. Irkhin, Soy. Phys. Solid State 13 {1972) 2035.
Journalof magnetism and magnetic materials
,~l
ELSEVIER
Transport properties of NdTNi3 H. K a d o m a t s u a'*, Y. Itoh b, H. F u k u d a ~, T. T s u t a o k a ~, T. T o k u n a g a ~ Cryogenic Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739, Japan bFacult~' of Liberal Arts Fukuyama University, Fukuyama 729-02, Japan FaculO, of School Education, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739, Japan
Abstract Electrical resistivity of Nd~Ni3 shows anomalies at the N6eI temperature TN = 29 K and the Curie temperature Tc = 14 K but does not show any change at the spin reorientation temperature Ta = 8.7 K. The thermoelectric power has also broad humps around 250 and 50 K as well as a sharp break at TN and a minimum at 10 K. The corresponding Hall coefficient shows anomalies at TN, Tc and TR, following the Curie-Weiss-Iaw-like behavior above TN. ~/ 1998 Elsevier Science B.V. All rights reserved.
Keywords: Transport properties; Thermoelectric power; Hall effect; Electrical resistivity - temperature dependence
In N d ; N i 3 the successive magnetic-phase transitions and metamagnetic transitions were found by magnetic studies [-ll. Together with the preliminary neutron diffraction study [2], it is expected that below TN = 29 K magnetic moment is in the c-plane, the magnetic periodicity is about three times lattice c, and the magnetic structure below Tc = 14 K is conical or canted. In 4f compounds conduction bands play an important role in the magnetic properties. Therefore the electrical resistivity p, thermoelectric power S and Hall coefficient Ru were investigated in this work. Fig. 1 shows p of NdvNis as a function of temperature T. The inset shows the R(T) curve up to 300 K. At TN and Tc remarkable and slight breaks appear. On the other hand, at the spin reorientation temperature TR = 8.7 K no anomaly is found. Above TN the temperature dependence of p shows a concave-downward curvature. In Fig. 2 is shown S of an isoelectronic compound LaTNis as a function of T in order to estimate the non-magnetic contribution to S in Nd~Nis. It is assumed that the S curve has two contributions, namely, a phonon drag term Sph and a non-magnetic Mott's diffusion term SnmE3], as schematically shown by dotted lines in Fig. 2. According to Burkov et al.'s model [4], the non-linear temperature dependence OfSnm indicates that Fermi level locates at the steep upward-slope in the density of states. *Corresponding author. Tel.: +81 824 24 6276; fax: + 81 824 24 0746; e-mail: [email protected].
TN
4o
NdTNi3
~ /.
-"
f--
og "~
.' 20
Tc
200
,
L ,
b ,
I
~0
TR . v~././/" •
07 T(K~
i
2~0
r
4r0
T(~ Fig. 1. Electrical resistivity p of NdvNi3 as a function of temperature T. The inset shows the p versus T curve up to 300 K.
kaTNi3
~2 . . . - ' o f "~'~- S ~
-~
1;0
T(K)
2;0
~oo
Fig. 2. Thermoelectric power S of LavNis as a function of temperature T. Some components to S are shown by dotted curves. For details see the text.
0304-8853/98/$19.00 £i,: 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 8 8 5 3 ( 9 7 ) 0 0 5 6 2 - 3
H. Kadomatsu et aL / Jom'nal of Magnetism and Magnetic Materials 177-181 (1998) tlt7-1118
1118
In Fig. 3 is shown S of NdvNi3 as a function of T. The inset shows S(T) up to 50 K. The S(T) curve shows broad humps around 250 and 50 K, a sharp break at TN and a minimum at 10 K. This S(T) curve can be decomposed into a magnetic term Sma~, a phonon drag term Sph, crystal-field effect term S~y and a MoWs diffusion term S,m, as schematically shown by dotted lines in Fig. 3. Fulde and Peschel [5] calculated S by taking account of crystal-field levels and found that So~yhas a peak near T = 0.35/k~ where ~5is crystal-field splitting energy and kB the Boltzmann constant. Unfortunately, we have no available data concerning the crystal field except for Ce~Nis [6]. The term shown by S#, + S~,y in Fig. 3 spreads over in a wider temperature range than Spt, of LaTNi3 (Fig. 2). The contribution of S m, may most likely overlap with Sp> AbeFskii and Irhkin [71 calculated S on the basis of the model that magnetic periodicity in antiferromagnetic ordering produces a magnetic Brillouin zone and an energy gap produced by this zone deforms the conduction band near the Fermi level. We followed their calculation but the result was different from the one obtained by them and it is as follows: +
Sm~g = + 3--57-~-~ t \(A - 1 ) 2
1- t + C
AC3:2
) ,
(1)
+2,,/1--t +B(1--t +C) where
t = T/TN,
A =I/kr,
(,,,kor~ )
= \ 2h2l
u~+ = +_(l-kv),
/,,kor~ k "~
'
c = \ -5p7-
V'
kF is Fermi wave vector and 1 is a magnetic wave vector. The meaning of the other symbols is given in Ref. ]-7]. However, Eq. (1) is qualitatively in agreement with one
6
~
L
NdzNi3
L'
=oL ~
T.
'
4
~ ~o r 20 T(~
"""
100
T(K)
200
40
300
Fig. 4. Hail coetScient RH of NdTNi3 as a function of temperature T. The inset shows RH{T) below 50 K.
obtained by Abel'skii and Irhkin. From the concaveupward curvature of the S(T) curve below TN, it is deduced that the conduction carrier has a hole-like character as a result of the appearance of magnetic Brillouin zone below TN. As seen from the inset, the effects of magnetic-phase transitions at Tt< and Tc to S modify Abel'skii and Irhkin's simple pictures. In Fig. 4 are shown the Hall coefficient RH of NdTNis as a function of T. Anomalies appear at TN, Tc and Try. The temperature dependence follows the Curie-Weiss law above TN. With a semi-empirical equation, the Hall coeiticient is written as RH = Ro + Re%, where Ro, RE and 7, are ordinary, extraordinary Hall coefficients and magnetic susceptibility, respectively. The value of R0 is estimated to be zero. However, RH of the isoelectronic LaTNi3, which is not described in this paper, is positive in sign in the temperature range 4.2K ~< T ~< 300 K and does not contradict the S result (hole character of conduction electron). In conclusion, in Nd,TNi3, the magnetic states are reflected considerably transport quantities p, S and RH. For obtaining the anisotropic information, experiments on the single crystal should be done.
References Nd7Ni3
E
3C
i
4
;
i
/
~
7 / / ".,, Sp +S~:,,z
TN
e2
Tel
[t] T. Tsutaoka, H. Fukuda, T. Tokunaga, H. Kadomatsu, Y. Itoh, J. Magn. Magn. Mater. 167 (1997) 248. [2] S. Kawano, Y. Ando, M. Kurisu, private communication. [3] F.J. Blatt, P.A. Schroeder, C.L. Foiles, D. Greig, Thermoelectric Power of Metals, Plenum Press, New York, 1976.
/S
m
/l~'°l
'~
0 I
100
,
T(K)
i b ~ ,
20
I
200
[ ,/
40 T(k3
300
Fig. 3. Thermoelectric power S of NdTNi3 as a function of temperature T. Some components to S are shown by dotted curves. For details see the text. The inset shows S(T) below 50 K.
[4] A.T. Burkov, E. Gratz, E. Bauer, R. Ressel, J. Alloys and Compounds 198 (1993) 1177. [5] P. Fulde, I. Peschel, Adv. Phys. 21 (1972) 1. [6] J.G. Sereni, O. Trovarelli, J.P. Kappler, C. Paschke, T. Trappmann, H. v. L6hneysen, Physics B 199&200 (1994) 567. [7] S.S. Abel'skii, Y.P. Irkhin, Soy. Phys. Solid State 13 {1972) 2035.