Successive Phase Transition at Ambient Pressure in CeCoSi: Single Crystal Studies

Magnetic Properties in Tetragonal Antiferromagnet CeCoSi

“…The magnetic field−temperature (H − T ) phase diagrams of (Ce x La 1−x )CoSi will be summarized later. In contrast to the sharp anomaly at T N , no clear anomaly is observed at T 0 in the electrical resistivity even in CeCoSi single crystal at ambient pressure [10]. While the anomaly at T 0 is clear in CeCoSi under pressures, that is obscure in (Ce 0.9 La 0.1 )CoSi even under pressures [11].…”

“…This indicates that the upper critical magnetic field of the phase III (H c ) is expected to lie just above H = 14.5 T in x = 0.7. Here, H c ∼ 20 T in x = 1 [10]. The magnetic field−temperature (H − T ) phase diagrams of (Ce x La 1−x )CoSi will be summarized later.…”

“…Above the pressure, it is rapidly suppressed and disappears at P C ∼ 2.2 GPa. Recently, we succeeded in synthesizing CeCoSi single crystals for the first time, and found a weak anomaly at T 0 ∼ 12 K at ambient pressure [10]. From the characteristics of the magnetization and the P − T phase diagram, we concluded that the intermediate phase for T N < T < T 0 is a part of the pressure induced ordered phase.…”

“…From the characteristics of the magnetization and the P − T phase diagram, we concluded that the intermediate phase for T N < T < T 0 is a part of the pressure induced ordered phase. A possibility of an antiferroquadrupolar (AFQ) ordering due to Ce-4 f electrons has been discussed for the origin of the intermediate phase [9][10][11]. Since there is no space-inversion symmetry on the Ce site, odd-parity multipoles could also contribute to form the phase transition at T 0 in addition to even-parity ones [10,11].…”

“…A possibility of an antiferroquadrupolar (AFQ) ordering due to Ce-4 f electrons has been discussed for the origin of the intermediate phase [9][10][11]. Since there is no space-inversion symmetry on the Ce site, odd-parity multipoles could also contribute to form the phase transition at T 0 in addition to even-parity ones [10,11]. Hereafter, we define the paramagnetic state above T 0 , possible multipole ordered state for T N < T < T 0 , and AFM ordered one below T N as phase I, II, and III, respectively.…”