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Antiferro–quadrupolar ordering in TmTe under high magnetic fields and high pressures
Physica B 281&282 (2000) 574}575
Antiferro}quadrupolar ordering in TmTe under high magnetic "elds and high pressures T. Tomita!, T. Goto!,*, S. Hane!, M. Ohashi!, T. Matsumura", N. Mori!, T. Suzuki! !Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8666, Japan "Department of Physics and Astronomy, University of College London, London WC1E 6BT, UK
Abstract The magnetization of TmTe along the [1 0 0] direction was measured under multiple extreme conditions of high magnetic "eld (B)17 T) and high pressure (P)1.2 GPa) and low temperature (¹*0.5 K). Anomalies due to the antiferro}quadrupolar transition were observed in the "eld and temperature dependencies of the magnetization and the B}¹ phase diagram was determined at various pressures. The phase diagram drastically changes with pressure and the change is found to be not uniform. ( 2000 Elsevier Science B.V. All rights reserved. Keywords: TmTe; Quadrupolar ordering; Magnetic phase diagram; High pressure
Thulium monochalcogenides TmX (X"S, Se and Te) with the NaCl structure show a large variety of electronic and magnetic properties. TmTe was believed to be a simple divalent semiconductor with localized 4f13 electrons. However, Matsumura et al. [1] found a transition by measuring the speci"c heat in zero and "nite magnetic "elds although the magnetic susceptibility exhibited no clear anomaly. The determined B}¹ phase diagram indicates that the transition temperature ¹ increases apparQ ently with magnetic "eld. These features are similar to the antiferro}quadrupolar (AFQ) transition in CeB [2]. 6 Later, Link et al. [3] made neutron di!raction study on TmTe and obtained a clear evidence for the occurrence of the AFQ ordering. Recently, Koyama et al. [4] have developed an instrument that makes high-resolution magnetization measurements under multiple extreme conditions of high pressure, high magnetic "eld and low temperature, which can detect a magnetic anomaly due to the AFQ transition in TmTe. In this study, we have measured with
* Corresponding author. Tel.: #81-3-3478-6811; fax: #813-3478-5471. E-mail address: [email protected] (T. Goto)
this instrument the magnetization of TmTe along the [1 0 0] direction at high pressures (P)1.2 GPa), high magnetic "elds (B)17 T) and low temperatures (¹*0.5 K) to clarify the mechanism of the AFQ ordering. Single crystals of TmTe were prepared by induction melting of high-purity constituents inside a tungsten crucible sealed in a vacuum. The magnetization was measured with the above instrument which consists of an extraction-type magnetometer and a nonmagnetic highpressure clamp cell made of Ti}Cu alloy, a 20 T superconducting magnet and a 3He refrigerator [4]. Fig. 1 shows the magnetization process for 0.5 K in high magnetic "elds up to 17 T along the [1 0 0] direction at various pressures. A small anomaly produced by the transition from the AFQ to the paramagnetic state can be seen in the magnetization process at 0, 0.3 and 0.6 GPa. No anomaly occurs at 1.2 GPa. (The AFQ state is stable in the low "eld region below the transition "eld B .) The anomaly is suppressed by the application of Q high pressure. The value of B increases with pressure. Q Fig. 2 shows the temperature dependence of the magnetization (M}¹ curve) in a magnetic "eld of 3.0 T along the [1 0 0] direction at various pressures. A small anomaly can also be seen on the M}¹ curve: the magnetization changes more rapidly just below the transition temperature ¹ . The anomaly is suppressed by the application Q
0921-4526/00/$ - see front matter ( 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 0 9 9 1 - 6
T. Tomita et al. / Physica B 281&282 (2000) 574}575
Fig. 1. Magnetization curves of TmTe for 0.5 K at several pressures. The arrow indicates B . Q
Fig. 2. Temperature dependence of the magnetization for 3 T at several pressures. The arrow indicates ¹ . Q
of high pressure. The value ¹ decreases with increasing Q pressure. We found that the magnetic "eld diminishes the anomaly on the M}¹ curve, which is consistent with the results of speci"c heat measurements in magnetic "elds [1]. Using the data of B and ¹ , we determined the B}¹ Q Q phase diagram for B [1 0 0] at various pressures, as @@ shown in Fig. 3. The value of ¹ in zero "eld is estimated Q for each pressure using the data determined by Tang et al. [5] from speci"c heat measurements at high pressures. The data of Matumura et al. for 0 GPa [1] are also plotted for comparison. Our phase diagram for ambient pressure is quite consistent with that of Matsumura et al. It should be noted that the B}¹ phase diagram drasti-
575
Fig. 3. Magnetic B}¹ phase diagram of TmTe. The data of Matsumura et al. [1] are also plotted.
cally changes by the application of high pressure and the change is not uniform: with increasing pressure, the region of the AFQ phase expands along the magnetic "eld axis, but shrinks along the temperature axis. In zero "eld, the change of ¹ is anomalous [5]. It "rst increases and Q then decreases. Recently, Hane et al. [6] measured the magnetization of Ce La B at high pressures, high 0.5 0.5 6 magnetic "elds and low temperatures and determined the B}¹ phase diagram. The region of the AFQ phase of Ce La B slightly expands uniformly with increasing 0.5 0.5 6 pressure. The change of the B}¹ diagram of TmTe by the application of high pressure is quite di!erent from that of Ce La B . The AFQ ordering in CeB is considered 0.5 0.5 6 6 to originate from the RKKY interaction [7]: the interaction between nearest-neighbor Ce ions is mediated by conduction electrons. In TmTe, however, the origin is not clari"ed yet. The di!erence in the change of the phase diagram observed between TmTe and Ce La B is 0.5 0.5 6 thought to come from the di!erence in the mechanism of the AFQ ordering.
References [1] T. Matsumura, S. Nakamura, T. Goto, H. Amitsuka, K. Matsuhira, T. Suzuki, J. Phys. Soc. Japan 67 (1998) 612. [2] T. Fujita, M. Suzuki, T. Komatsubara, S. Kunii, T. Kasuya, T. Ohtsuka, J. Phys. Soc. Japan 35 (1980) 569. [3] P. Link, A. Gukasov, J.M. Mignot, T. Matsumura, T. Suzuki, Phys. Rev. Lett. 80 (1998) 4779. [4] K. Koyama, S. Hane, K. Kamishima, T. Goto, Rev. Sci. Instr. 69 (1998) 3009. [5] Tang et al., private communication. [6] S. Hane et al., private communication. [7] F.J. Ohkawa, J. Phys. Soc. Japan 54 (1985) 3909.
Antiferro}quadrupolar ordering in TmTe under high magnetic "elds and high pressures T. Tomita!, T. Goto!,*, S. Hane!, M. Ohashi!, T. Matsumura", N. Mori!, T. Suzuki! !Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8666, Japan "Department of Physics and Astronomy, University of College London, London WC1E 6BT, UK
Abstract The magnetization of TmTe along the [1 0 0] direction was measured under multiple extreme conditions of high magnetic "eld (B)17 T) and high pressure (P)1.2 GPa) and low temperature (¹*0.5 K). Anomalies due to the antiferro}quadrupolar transition were observed in the "eld and temperature dependencies of the magnetization and the B}¹ phase diagram was determined at various pressures. The phase diagram drastically changes with pressure and the change is found to be not uniform. ( 2000 Elsevier Science B.V. All rights reserved. Keywords: TmTe; Quadrupolar ordering; Magnetic phase diagram; High pressure
Thulium monochalcogenides TmX (X"S, Se and Te) with the NaCl structure show a large variety of electronic and magnetic properties. TmTe was believed to be a simple divalent semiconductor with localized 4f13 electrons. However, Matsumura et al. [1] found a transition by measuring the speci"c heat in zero and "nite magnetic "elds although the magnetic susceptibility exhibited no clear anomaly. The determined B}¹ phase diagram indicates that the transition temperature ¹ increases apparQ ently with magnetic "eld. These features are similar to the antiferro}quadrupolar (AFQ) transition in CeB [2]. 6 Later, Link et al. [3] made neutron di!raction study on TmTe and obtained a clear evidence for the occurrence of the AFQ ordering. Recently, Koyama et al. [4] have developed an instrument that makes high-resolution magnetization measurements under multiple extreme conditions of high pressure, high magnetic "eld and low temperature, which can detect a magnetic anomaly due to the AFQ transition in TmTe. In this study, we have measured with
* Corresponding author. Tel.: #81-3-3478-6811; fax: #813-3478-5471. E-mail address: [email protected] (T. Goto)
this instrument the magnetization of TmTe along the [1 0 0] direction at high pressures (P)1.2 GPa), high magnetic "elds (B)17 T) and low temperatures (¹*0.5 K) to clarify the mechanism of the AFQ ordering. Single crystals of TmTe were prepared by induction melting of high-purity constituents inside a tungsten crucible sealed in a vacuum. The magnetization was measured with the above instrument which consists of an extraction-type magnetometer and a nonmagnetic highpressure clamp cell made of Ti}Cu alloy, a 20 T superconducting magnet and a 3He refrigerator [4]. Fig. 1 shows the magnetization process for 0.5 K in high magnetic "elds up to 17 T along the [1 0 0] direction at various pressures. A small anomaly produced by the transition from the AFQ to the paramagnetic state can be seen in the magnetization process at 0, 0.3 and 0.6 GPa. No anomaly occurs at 1.2 GPa. (The AFQ state is stable in the low "eld region below the transition "eld B .) The anomaly is suppressed by the application of Q high pressure. The value of B increases with pressure. Q Fig. 2 shows the temperature dependence of the magnetization (M}¹ curve) in a magnetic "eld of 3.0 T along the [1 0 0] direction at various pressures. A small anomaly can also be seen on the M}¹ curve: the magnetization changes more rapidly just below the transition temperature ¹ . The anomaly is suppressed by the application Q
0921-4526/00/$ - see front matter ( 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 0 9 9 1 - 6
T. Tomita et al. / Physica B 281&282 (2000) 574}575
Fig. 1. Magnetization curves of TmTe for 0.5 K at several pressures. The arrow indicates B . Q
Fig. 2. Temperature dependence of the magnetization for 3 T at several pressures. The arrow indicates ¹ . Q
of high pressure. The value ¹ decreases with increasing Q pressure. We found that the magnetic "eld diminishes the anomaly on the M}¹ curve, which is consistent with the results of speci"c heat measurements in magnetic "elds [1]. Using the data of B and ¹ , we determined the B}¹ Q Q phase diagram for B [1 0 0] at various pressures, as @@ shown in Fig. 3. The value of ¹ in zero "eld is estimated Q for each pressure using the data determined by Tang et al. [5] from speci"c heat measurements at high pressures. The data of Matumura et al. for 0 GPa [1] are also plotted for comparison. Our phase diagram for ambient pressure is quite consistent with that of Matsumura et al. It should be noted that the B}¹ phase diagram drasti-
575
Fig. 3. Magnetic B}¹ phase diagram of TmTe. The data of Matsumura et al. [1] are also plotted.
cally changes by the application of high pressure and the change is not uniform: with increasing pressure, the region of the AFQ phase expands along the magnetic "eld axis, but shrinks along the temperature axis. In zero "eld, the change of ¹ is anomalous [5]. It "rst increases and Q then decreases. Recently, Hane et al. [6] measured the magnetization of Ce La B at high pressures, high 0.5 0.5 6 magnetic "elds and low temperatures and determined the B}¹ phase diagram. The region of the AFQ phase of Ce La B slightly expands uniformly with increasing 0.5 0.5 6 pressure. The change of the B}¹ diagram of TmTe by the application of high pressure is quite di!erent from that of Ce La B . The AFQ ordering in CeB is considered 0.5 0.5 6 6 to originate from the RKKY interaction [7]: the interaction between nearest-neighbor Ce ions is mediated by conduction electrons. In TmTe, however, the origin is not clari"ed yet. The di!erence in the change of the phase diagram observed between TmTe and Ce La B is 0.5 0.5 6 thought to come from the di!erence in the mechanism of the AFQ ordering.
References [1] T. Matsumura, S. Nakamura, T. Goto, H. Amitsuka, K. Matsuhira, T. Suzuki, J. Phys. Soc. Japan 67 (1998) 612. [2] T. Fujita, M. Suzuki, T. Komatsubara, S. Kunii, T. Kasuya, T. Ohtsuka, J. Phys. Soc. Japan 35 (1980) 569. [3] P. Link, A. Gukasov, J.M. Mignot, T. Matsumura, T. Suzuki, Phys. Rev. Lett. 80 (1998) 4779. [4] K. Koyama, S. Hane, K. Kamishima, T. Goto, Rev. Sci. Instr. 69 (1998) 3009. [5] Tang et al., private communication. [6] S. Hane et al., private communication. [7] F.J. Ohkawa, J. Phys. Soc. Japan 54 (1985) 3909.