- Email: [email protected]
Magnetization and dHvA effect study of the rare-earth monopnictides in high magnetic fields
Journal of Magnetism and Magnetic Materials 177 181 (1998) 355-356
~i Jeurnalof mnalnousm magneUc ~i materials
ELSEVIER
Magnetization and dHvA effect study of the rare-earth monopnictides in high magnetic fields T. Sakon a'*, Y. Nakanishi a, M. Ozawa b, H. Nojiri a, T. Suzuki b, M.
Motokawa
a
alnstitutefor Materials Research, Tohoku University, Sendai 980-77, Japan UDepartment of Physics, Faculty of Science, Tohoku University, Sendai 980-77, Japan
Abstract
Magnetization measurements of TbSb have been studied in pulsed high magnetic fields up to 30 T. When an external magnetic field H is applied parallel to easy axis [1 1 1], three steps are observed in magnetization process. This suggests complicated magnetic structures in high fields due to electric quadrupole moments. We have also studied dHvA effect of TbSb in high magnetic fields up to 23 T, and observed large spin splittings. From these experimental results, the c-f exchange interaction is estimated to be about 37 meV for H HI-10 03, which means the exchange interaction between carriers and 4f electrons is strong. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Rare-earth pnictides; Magnetization - measurements; De Haas-van Alphen effect; High magnetic field
Rare-earth monopnictides have the simple cubic NaCl-type structure and show a variety of magnetic properties. Some rare-earth antimonides (ReSb) represent interesting properties due to competition among the magnetic exchange interaction, crystal electric field and quadrupole interactions. F o r example, CeSb shows 14 magnetic phases in H T diagram [1], which is explained by the A N N N I model [2]. On the other hand, DySb is a typical example which shows HoP-type quadrupole interaction [3]. However there has been a few information of TbSb. TbSb shows an antiferromagnetic transition and trigonal distortion simultaneously at TN = 15.5 K [4, 5]. In the A F state, the magnetic moments are aligned ferromagnetieally in the (1 1 1) plane and antiferromagnetically in the adjacent layers pointing to the rl 1 1] direction. In this compound, complicated magnetic structures are expected to be realized in a magnetic field due to quadrupole interaction. We have performed measurements of magnetization and dHvA effect up to 30 T using pulsed fields and 23 T using steady fields, respectively, in
order to investigate the magnetic properties and interaction between carriers and 4f electrons. Magnetization process of a single-crystal TbSb at T = 4.2 K are shown in Fig. 1. When an external field is applied parallel to the [1 1 1] axis, three sharp steps is clearly observed. To make these steps clear, the differential magnetization dM/dH for HII[1 1 1] is shown in an inset of Fig. 1. The induced magnetization increases up to 9 laB/Tb, which is supposed to be the full moment of Tb 3+ ion, and saturates at 16 T. For other two directions, only one step is observed. F o r HII[I 1 1], when the
'°I 8
oL/ 0
* Corresponding author. Tel.: + 81 22 215 2017; fax: + 81 22 215 2016; e-maih [email protected].
TbSb
5
,
.....
10
15 H (tesla)
Erii t
20
....
25
,,J
30
Fig. 1. Magnetization process of TbSb at T = 4.2 K in a pulsed magnetic field. Arrows indicate the steps for H]I[1 1 1]. Inset shows the differential magnetization.
0304-8853/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 88 5 3 ( 9 7 ) 0 0 9 5 0 - 5
356
T. Sakon et al, / Journal of Magnetism and Magnetic Materials 177-181 (1998) 355-356
temperature is increased, the highest critical field//ca is constant up to 10 K, while Hca and Hc2 are slightly decrease above 6 K. In the case of DySb, which is the typical quadrupole ordering system and shows antiferromagnetic order below TN 9.5 K, two sharp steps are observed when a magnetic field is applied to the E1 0 01 axis [6]. For H < 2 T, the type II AF structure is realized and magnetization is small in magnitude. In a field range of 2 T < H < 4.5 T the induced moment is about 5 ~tB/Dy, a half of the full moment of Dy 3+ (gj J = 10 ~tB/Dy) and it indicates a HoP-type quadrupole state is realized. Neutron-scattering experiments also suggest this magnetic structure [7]. At 5 T the induced magnetic moment increases steeply up to 10 #R/Dy and saturates at 25 T, suggesting that the ferrimagnetic state is realized. The magnetization process shows large anisotropy. For Hill1 1 01 or [1 1 11, only one sharp step is observed. The magnetization and neutron experiments indicate that the magnetic moments are fixed parallel to the [1 0 0] axis even if an external magnetic field is applied to [1 1 0] or [1 1 11 axis. It suggests a strong quadrupole interaction acts on DySb. The anisotropy of the induced magnetization of TbSb is smaller than that of DySb. Therefore, we can believe the quadrupole interaction is much smaller than that of TbSb. On the other hand, the dHvA effect of TbSb was studied for H <~ 23 T and the oscillation was observed above 1.5 T and even at temperatures as high as 6 K, which means the sample quality is high. We observed beats dearly, which come from spin splitting. The F F T spectra of dHvA oscillation are illustrated in Fig. 2. The width of splitting of ct and fl branches increased with increasing field. Using the results of dHvA effect and magnetization measurements, we estimate the intensity of the c-f exchange interaction. The details of the calculation is described in Refs. [8, 9]. For Ht[[1 00], it is about 37 meV. It reveals that the exchange interaction between carriers and 4f electrons are much strong and it is comparable with that of TmSb [101. On the other hand, the shape of Fermi surface of TbSb is different from that of DySb, which shows large anisotropy due to strong quadrupole interaction, and is rather similar to that of LaSb [61. In conclusion, the induced magnetization of TbSb in an external magnetic field parallel to the easy axis (Hf[[1 1 1]) show three steps, which suggests complicated magnetic structure in magnetic fields due to electric quadrupole moments. The dHvA effect of TbSb in high magnetic fields up to 23 T shows large spin splitting. From these results, the exchange interaction between
. . . .
i
t
. . . .
i
. . . .
i
. . . .
TbSbH//[IO0] 2.5T
=
e-
,~
3T
ID
AA ,B,
0
11T
500 1000 1500 2000 Frequency (tesla)
Fig. 2. FFT spectra ofdHvA oscillation on TbSb at T = 1.5 K.
carriers and 4f electrons is supposed to be strong. The quadrupole interaction of TbSb is much smaller than that of DySb.
References [1] J. Rossat-Mignod, P. Burlet, H. Bartholin, O. Vogt, R. Lagnier, J. Phys. C 13 (1980) 6381. 1-2] T. Kasuya, Y.S. Kwon, T. Suzuki, K. Nakanishi, F. Ishikawa, K. Takegahara, J. Magn. Magn. Mater. 90&91 (1990) 389. [3] G. Busch, O. Vogt, J. Appl. Phys. 39 (1968) 1334. 1-4] A. Buschbeck, Ch. Chojnowski, J. Kotzler, R. Sonder, G. Thummes, J. Magn. Magn. Mater. 69 (1987) 171. 1-51 F. Hullinger, F. Stucki, Z. Phys. B 31 (1978) 391. 1-6] M. Ozawa, T. Matsumura, A. Uesawa, H. Aoki, H. Shida, T. Sakon, Y. Nakanishi, H. Nojiri, M. Motokawa, T. Suzuki, Physica B 230-232 (1997) 744. 1-7"1 H.R. Child, M.K. Wilkinson, J.W. Cable, W.C. Koehler, E.O. Wollan, Phys. Rev. 131 (1963) 922. [8"1 M. Wulff, Doctor Thesis, Cambridge University, 1985. 1-9] M. Wulff, G.G. Lonzarich, D. Fort, H.L. Skriver, Europhys. Lett. 7 (1988) 629. 1-10"1 S. Nimori, Doctor Thesis, Tohoku University, 1994.
~i Jeurnalof mnalnousm magneUc ~i materials
ELSEVIER
Magnetization and dHvA effect study of the rare-earth monopnictides in high magnetic fields T. Sakon a'*, Y. Nakanishi a, M. Ozawa b, H. Nojiri a, T. Suzuki b, M.
Motokawa
a
alnstitutefor Materials Research, Tohoku University, Sendai 980-77, Japan UDepartment of Physics, Faculty of Science, Tohoku University, Sendai 980-77, Japan
Abstract
Magnetization measurements of TbSb have been studied in pulsed high magnetic fields up to 30 T. When an external magnetic field H is applied parallel to easy axis [1 1 1], three steps are observed in magnetization process. This suggests complicated magnetic structures in high fields due to electric quadrupole moments. We have also studied dHvA effect of TbSb in high magnetic fields up to 23 T, and observed large spin splittings. From these experimental results, the c-f exchange interaction is estimated to be about 37 meV for H HI-10 03, which means the exchange interaction between carriers and 4f electrons is strong. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Rare-earth pnictides; Magnetization - measurements; De Haas-van Alphen effect; High magnetic field
Rare-earth monopnictides have the simple cubic NaCl-type structure and show a variety of magnetic properties. Some rare-earth antimonides (ReSb) represent interesting properties due to competition among the magnetic exchange interaction, crystal electric field and quadrupole interactions. F o r example, CeSb shows 14 magnetic phases in H T diagram [1], which is explained by the A N N N I model [2]. On the other hand, DySb is a typical example which shows HoP-type quadrupole interaction [3]. However there has been a few information of TbSb. TbSb shows an antiferromagnetic transition and trigonal distortion simultaneously at TN = 15.5 K [4, 5]. In the A F state, the magnetic moments are aligned ferromagnetieally in the (1 1 1) plane and antiferromagnetically in the adjacent layers pointing to the rl 1 1] direction. In this compound, complicated magnetic structures are expected to be realized in a magnetic field due to quadrupole interaction. We have performed measurements of magnetization and dHvA effect up to 30 T using pulsed fields and 23 T using steady fields, respectively, in
order to investigate the magnetic properties and interaction between carriers and 4f electrons. Magnetization process of a single-crystal TbSb at T = 4.2 K are shown in Fig. 1. When an external field is applied parallel to the [1 1 1] axis, three sharp steps is clearly observed. To make these steps clear, the differential magnetization dM/dH for HII[1 1 1] is shown in an inset of Fig. 1. The induced magnetization increases up to 9 laB/Tb, which is supposed to be the full moment of Tb 3+ ion, and saturates at 16 T. For other two directions, only one step is observed. F o r HII[I 1 1], when the
'°I 8
oL/ 0
* Corresponding author. Tel.: + 81 22 215 2017; fax: + 81 22 215 2016; e-maih [email protected].
TbSb
5
,
.....
10
15 H (tesla)
Erii t
20
....
25
,,J
30
Fig. 1. Magnetization process of TbSb at T = 4.2 K in a pulsed magnetic field. Arrows indicate the steps for H]I[1 1 1]. Inset shows the differential magnetization.
0304-8853/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 88 5 3 ( 9 7 ) 0 0 9 5 0 - 5
356
T. Sakon et al, / Journal of Magnetism and Magnetic Materials 177-181 (1998) 355-356
temperature is increased, the highest critical field//ca is constant up to 10 K, while Hca and Hc2 are slightly decrease above 6 K. In the case of DySb, which is the typical quadrupole ordering system and shows antiferromagnetic order below TN 9.5 K, two sharp steps are observed when a magnetic field is applied to the E1 0 01 axis [6]. For H < 2 T, the type II AF structure is realized and magnetization is small in magnitude. In a field range of 2 T < H < 4.5 T the induced moment is about 5 ~tB/Dy, a half of the full moment of Dy 3+ (gj J = 10 ~tB/Dy) and it indicates a HoP-type quadrupole state is realized. Neutron-scattering experiments also suggest this magnetic structure [7]. At 5 T the induced magnetic moment increases steeply up to 10 #R/Dy and saturates at 25 T, suggesting that the ferrimagnetic state is realized. The magnetization process shows large anisotropy. For Hill1 1 01 or [1 1 11, only one sharp step is observed. The magnetization and neutron experiments indicate that the magnetic moments are fixed parallel to the [1 0 0] axis even if an external magnetic field is applied to [1 1 0] or [1 1 11 axis. It suggests a strong quadrupole interaction acts on DySb. The anisotropy of the induced magnetization of TbSb is smaller than that of DySb. Therefore, we can believe the quadrupole interaction is much smaller than that of TbSb. On the other hand, the dHvA effect of TbSb was studied for H <~ 23 T and the oscillation was observed above 1.5 T and even at temperatures as high as 6 K, which means the sample quality is high. We observed beats dearly, which come from spin splitting. The F F T spectra of dHvA oscillation are illustrated in Fig. 2. The width of splitting of ct and fl branches increased with increasing field. Using the results of dHvA effect and magnetization measurements, we estimate the intensity of the c-f exchange interaction. The details of the calculation is described in Refs. [8, 9]. For Ht[[1 00], it is about 37 meV. It reveals that the exchange interaction between carriers and 4f electrons are much strong and it is comparable with that of TmSb [101. On the other hand, the shape of Fermi surface of TbSb is different from that of DySb, which shows large anisotropy due to strong quadrupole interaction, and is rather similar to that of LaSb [61. In conclusion, the induced magnetization of TbSb in an external magnetic field parallel to the easy axis (Hf[[1 1 1]) show three steps, which suggests complicated magnetic structure in magnetic fields due to electric quadrupole moments. The dHvA effect of TbSb in high magnetic fields up to 23 T shows large spin splitting. From these results, the exchange interaction between
. . . .
i
t
. . . .
i
. . . .
i
. . . .
TbSbH//[IO0] 2.5T
=
e-
,~
3T
ID
AA ,B,
0
11T
500 1000 1500 2000 Frequency (tesla)
Fig. 2. FFT spectra ofdHvA oscillation on TbSb at T = 1.5 K.
carriers and 4f electrons is supposed to be strong. The quadrupole interaction of TbSb is much smaller than that of DySb.
References [1] J. Rossat-Mignod, P. Burlet, H. Bartholin, O. Vogt, R. Lagnier, J. Phys. C 13 (1980) 6381. 1-2] T. Kasuya, Y.S. Kwon, T. Suzuki, K. Nakanishi, F. Ishikawa, K. Takegahara, J. Magn. Magn. Mater. 90&91 (1990) 389. [3] G. Busch, O. Vogt, J. Appl. Phys. 39 (1968) 1334. 1-4] A. Buschbeck, Ch. Chojnowski, J. Kotzler, R. Sonder, G. Thummes, J. Magn. Magn. Mater. 69 (1987) 171. 1-51 F. Hullinger, F. Stucki, Z. Phys. B 31 (1978) 391. 1-6] M. Ozawa, T. Matsumura, A. Uesawa, H. Aoki, H. Shida, T. Sakon, Y. Nakanishi, H. Nojiri, M. Motokawa, T. Suzuki, Physica B 230-232 (1997) 744. 1-7"1 H.R. Child, M.K. Wilkinson, J.W. Cable, W.C. Koehler, E.O. Wollan, Phys. Rev. 131 (1963) 922. [8"1 M. Wulff, Doctor Thesis, Cambridge University, 1985. 1-9] M. Wulff, G.G. Lonzarich, D. Fort, H.L. Skriver, Europhys. Lett. 7 (1988) 629. 1-10"1 S. Nimori, Doctor Thesis, Tohoku University, 1994.