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Magnetic field and pressure effects in Ce3Al11
ARTICLE IN PRESS
Physica B 359–361 (2005) 272–274 www.elsevier.com/locate/physb
Magnetic field and pressure effects in Ce3Al11 Takao Ebiharaa,, Tetsuro Takahashia, Koji Tezukaa, Masato Hedob, Yoshiya Uwatokob, Shinya Ujic a
Department of Physics, Faculty of Science Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan b Institute for Solid State Physics, Chiba 277-8581, Japan c National Institute for Materials Science, Ibaraki 305-0003, Japan
Abstract We measured electrical resistivity under magnetic field ðo13:5 TÞ and pressure ðo3 GPaÞ in Ce3 Al11 to study anomalies at 3.2 and 6.3 K in zero field and ambient pressure. Transverse magnetoresistance shows that Ce3 Al11 behaves like a standard Kondo material after the two anomalies disappear. With applied pressure, the low-temperature anomaly moves down to lower temperature very rapidly. After the low-temperature anomaly is suppressed, hightemperature anomaly still stands at almost the same temperature (6.3 K). Ce3 Al11 behaves like a ferromagnet with Kondo behavior from the stand point of electrical resistivity under pressure. r 2005 Elsevier B.V. All rights reserved. PACS: 75.47.m; 74.62.Fj; 75.30.Kz Keywords: Ce3 Al11 ; Transverse magnetoresistance; Pressure
It was found in the recent years that some rare earth or uranium compounds show superconductivity after magnetic ordering is suppressed by pressure. Earliest examples were reported in heavy fermion antiferromagnet CeIn3 and CePd2 Si2 by Mathur et al. [1]. In uranium compounds, it is observed that UGe2 shows superconductivity after suppression of ferromagnetic ordering by pressure Corresponding
author. Tel.: +81 54 238 4739; fax: +81 54 238 0993. E-mail address: [email protected] (T. Ebihara).
[2] and superconductivity coexists with ferromagnetism in URhGe [3]. Various s–f electron systems play an important role in Ce and U compounds. The current focus is on whether Ce ferromagnetic compounds show superconductivity. Ce3 Al11 ; which orders ferromagnetically at 6.3 K and into an incommensurate phase at 3.2 K, crystallizes into La3 Al11 -type orthorhombic crystal structure. By magnetometric and neutron diffraction experiments, the magnetic structure is determined. Ce3 Al11 possesses two unequivalent Ce cites; one cite ðCeI Þ orders magnetically and the
0921-4526/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2005.01.074
ARTICLE IN PRESS T. Ebihara et al. / Physica B 359– 361 (2005) 272–274
50
Ce3Al11
1.8GPa
40
ρ (µΩ cm)
T1 T2
30 0.8GPa
3.1GPa
20 0GPa
2.6GPa
10
0
1
10
100
T(K) Fig. 2. Temperature dependence of electrical resistivity in Ce3 Al11 under pressure.
10
T1 8
T2
6
T(K)
other ðCeII Þ owes Kondo scattering. The moment at CeI is 1:27mB and at CeII is 0:24mB : In this work, pressure and magnetic field effect in electrical resistivity in Ce3 Al11 are reported [4–6]. The Ce3 Al11 single crystal was grown by the flux-method with excess of Al. An excess of Al was removed by NaOH solution. Typical dimensions of the crystals were 2 2 6 mm3 : The electrical resistivities under pressure and in magnetic field were measured by the standard four-probe AC and DC method, respectively. Intender-type piston cylinder was used as pressure cell. Magnetoresistance was measured in a 15 T-superconducting magnet above 1.5 K. In Fig. 1, transverse magnetoresistance data of Ce3 Al11 are shown. The two anomalies related with two magnetic phase transitions at 6.3 ðT1 Þ and 3.2 K ðT2 Þ were observed at 0 T. T2 shifts to lower temperatures with increasing magnetic field and disappears above 4 T and T1 fades out with increasing magnetic field. Above 6 T, Ce3 Al11 behaves like a standard heavy fermion because Ce3 Al11 is already in the ferromagnetic state. In Fig. 2, pressure-dependent electrical resistivity is shown. Although the sharp peak at T2 is broadened by pressure and disappears rapidly at 1.8 GPa, T1 remains at the same temperature. Double peaks at ambient pressure in electrical
273
4
500 Ce3Al11 J//a-axis J=20mA
400
2
ρ (µΩ cm)
T1
0
300
0
'ρ (0T)' 'ρ (1T)'
T2
200
1
2
3
4
P(GPa)
'ρ (2T)'
Fig. 3. Pressure–temperature phase diagram in Ce3 Al11 :
'ρ (4T)' 'ρ (6T)' 'ρ (8T)'
100
'ρ (10T)' 'ρ (12T)' 'ρ (13.5T)'
0
0
5
10
15
20
Temperature (K) Fig. 1. Transverse magnetoresistance in Ce3 Al11 at ambient pressure.
resistivity become one in the experimental temperature window. In Fig. 3, we present transition temperatures versus pressure. Solid squares and circles show T1 and T2 ; respectively. Solid curves are guides to the eye. Although T2 is expected to be suppressed about 3.2 GPa, T1 gradually increases its
ARTICLE IN PRESS 274
T. Ebihara et al. / Physica B 359– 361 (2005) 272–274
temperature with increasing field. However, at much higher pressure, T1 decreases. Gradual change of T1 may be a consequence of reduced correlation between CeI and CeII moments because of suppression of CeII moments [7]. Yet the behavior of T1 is a little different from earlier results. We should take into account that a cubic anvil cell used for earlier results is not good at controlling low pressure. The earlier results show that T1 decreases again at higher pressures. In summary, we observed magnetic field and pressure effects in the electrical resistivity of Ce3 Al11 : T1 does not change very much but T2 disappears rapidly with increasing magnetic field or pressure. With respect to the electrical resistivity measurements under pressure, the P–T phase diagram below 3.5 GPa was drawn. One of the authors (T.E.) is supported by Casio Science Promotion Foundation and Corning
Japan. T.E. also expresses many thanks to Suzuki Foundation and Y. Momose of Research Institute of Electronics, Shizuoka University. Works at National Institute for Materials Science and Institute of Solid State Physics in Japan were done under the auspices of MEXT.
References [1] [2] [3] [4] [5]
N.D. Matur, et al., Nature 394 (1998) 39. S.S. Saxena, et al., Nature 406 (1998) 587. D. Aoki, et al., Nature 413 (1998) 613. J.X. Boucherle, et al., Physica B 234–236 (1997) 687. A. Mun˜oz, et al., J. Phys.: Condens. Matter 7 (1995) 8821. [6] J.X. Boucherle, et al., J. Magn. Magn. Mater. 148 (1997) 397. [7] T. Ebihara, et al., J. Magn. Magn. Mater. 272–276 (2004) E83.
Physica B 359–361 (2005) 272–274 www.elsevier.com/locate/physb
Magnetic field and pressure effects in Ce3Al11 Takao Ebiharaa,, Tetsuro Takahashia, Koji Tezukaa, Masato Hedob, Yoshiya Uwatokob, Shinya Ujic a
Department of Physics, Faculty of Science Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan b Institute for Solid State Physics, Chiba 277-8581, Japan c National Institute for Materials Science, Ibaraki 305-0003, Japan
Abstract We measured electrical resistivity under magnetic field ðo13:5 TÞ and pressure ðo3 GPaÞ in Ce3 Al11 to study anomalies at 3.2 and 6.3 K in zero field and ambient pressure. Transverse magnetoresistance shows that Ce3 Al11 behaves like a standard Kondo material after the two anomalies disappear. With applied pressure, the low-temperature anomaly moves down to lower temperature very rapidly. After the low-temperature anomaly is suppressed, hightemperature anomaly still stands at almost the same temperature (6.3 K). Ce3 Al11 behaves like a ferromagnet with Kondo behavior from the stand point of electrical resistivity under pressure. r 2005 Elsevier B.V. All rights reserved. PACS: 75.47.m; 74.62.Fj; 75.30.Kz Keywords: Ce3 Al11 ; Transverse magnetoresistance; Pressure
It was found in the recent years that some rare earth or uranium compounds show superconductivity after magnetic ordering is suppressed by pressure. Earliest examples were reported in heavy fermion antiferromagnet CeIn3 and CePd2 Si2 by Mathur et al. [1]. In uranium compounds, it is observed that UGe2 shows superconductivity after suppression of ferromagnetic ordering by pressure Corresponding
author. Tel.: +81 54 238 4739; fax: +81 54 238 0993. E-mail address: [email protected] (T. Ebihara).
[2] and superconductivity coexists with ferromagnetism in URhGe [3]. Various s–f electron systems play an important role in Ce and U compounds. The current focus is on whether Ce ferromagnetic compounds show superconductivity. Ce3 Al11 ; which orders ferromagnetically at 6.3 K and into an incommensurate phase at 3.2 K, crystallizes into La3 Al11 -type orthorhombic crystal structure. By magnetometric and neutron diffraction experiments, the magnetic structure is determined. Ce3 Al11 possesses two unequivalent Ce cites; one cite ðCeI Þ orders magnetically and the
0921-4526/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2005.01.074
ARTICLE IN PRESS T. Ebihara et al. / Physica B 359– 361 (2005) 272–274
50
Ce3Al11
1.8GPa
40
ρ (µΩ cm)
T1 T2
30 0.8GPa
3.1GPa
20 0GPa
2.6GPa
10
0
1
10
100
T(K) Fig. 2. Temperature dependence of electrical resistivity in Ce3 Al11 under pressure.
10
T1 8
T2
6
T(K)
other ðCeII Þ owes Kondo scattering. The moment at CeI is 1:27mB and at CeII is 0:24mB : In this work, pressure and magnetic field effect in electrical resistivity in Ce3 Al11 are reported [4–6]. The Ce3 Al11 single crystal was grown by the flux-method with excess of Al. An excess of Al was removed by NaOH solution. Typical dimensions of the crystals were 2 2 6 mm3 : The electrical resistivities under pressure and in magnetic field were measured by the standard four-probe AC and DC method, respectively. Intender-type piston cylinder was used as pressure cell. Magnetoresistance was measured in a 15 T-superconducting magnet above 1.5 K. In Fig. 1, transverse magnetoresistance data of Ce3 Al11 are shown. The two anomalies related with two magnetic phase transitions at 6.3 ðT1 Þ and 3.2 K ðT2 Þ were observed at 0 T. T2 shifts to lower temperatures with increasing magnetic field and disappears above 4 T and T1 fades out with increasing magnetic field. Above 6 T, Ce3 Al11 behaves like a standard heavy fermion because Ce3 Al11 is already in the ferromagnetic state. In Fig. 2, pressure-dependent electrical resistivity is shown. Although the sharp peak at T2 is broadened by pressure and disappears rapidly at 1.8 GPa, T1 remains at the same temperature. Double peaks at ambient pressure in electrical
273
4
500 Ce3Al11 J//a-axis J=20mA
400
2
ρ (µΩ cm)
T1
0
300
0
'ρ (0T)' 'ρ (1T)'
T2
200
1
2
3
4
P(GPa)
'ρ (2T)'
Fig. 3. Pressure–temperature phase diagram in Ce3 Al11 :
'ρ (4T)' 'ρ (6T)' 'ρ (8T)'
100
'ρ (10T)' 'ρ (12T)' 'ρ (13.5T)'
0
0
5
10
15
20
Temperature (K) Fig. 1. Transverse magnetoresistance in Ce3 Al11 at ambient pressure.
resistivity become one in the experimental temperature window. In Fig. 3, we present transition temperatures versus pressure. Solid squares and circles show T1 and T2 ; respectively. Solid curves are guides to the eye. Although T2 is expected to be suppressed about 3.2 GPa, T1 gradually increases its
ARTICLE IN PRESS 274
T. Ebihara et al. / Physica B 359– 361 (2005) 272–274
temperature with increasing field. However, at much higher pressure, T1 decreases. Gradual change of T1 may be a consequence of reduced correlation between CeI and CeII moments because of suppression of CeII moments [7]. Yet the behavior of T1 is a little different from earlier results. We should take into account that a cubic anvil cell used for earlier results is not good at controlling low pressure. The earlier results show that T1 decreases again at higher pressures. In summary, we observed magnetic field and pressure effects in the electrical resistivity of Ce3 Al11 : T1 does not change very much but T2 disappears rapidly with increasing magnetic field or pressure. With respect to the electrical resistivity measurements under pressure, the P–T phase diagram below 3.5 GPa was drawn. One of the authors (T.E.) is supported by Casio Science Promotion Foundation and Corning
Japan. T.E. also expresses many thanks to Suzuki Foundation and Y. Momose of Research Institute of Electronics, Shizuoka University. Works at National Institute for Materials Science and Institute of Solid State Physics in Japan were done under the auspices of MEXT.
References [1] [2] [3] [4] [5]
N.D. Matur, et al., Nature 394 (1998) 39. S.S. Saxena, et al., Nature 406 (1998) 587. D. Aoki, et al., Nature 413 (1998) 613. J.X. Boucherle, et al., Physica B 234–236 (1997) 687. A. Mun˜oz, et al., J. Phys.: Condens. Matter 7 (1995) 8821. [6] J.X. Boucherle, et al., J. Magn. Magn. Mater. 148 (1997) 397. [7] T. Ebihara, et al., J. Magn. Magn. Mater. 272–276 (2004) E83.