High Field ESR of the Frustrated Antiferromagnet Ba₂Sn₂Ga₃ZnCr₇O₂₂on a Pyrochlore Slab

Abstract

High field ESR measurements of pyrochlore slab antiferromagnets Ba 2 Sn 2 Ga 3+x ZnCr 7−x O 22 (x=0,1, 3, 5, 6.9) have been performed in the millimeter wave region at temperatures from 4.2 K to 200 K. For Ba 2 Sn 2 Ga 3 ZnCr 7 O 22 (x = 0), the pyrochlore slab is fully filled with Cr 3+ ions, the line width of the ESR absorption line increased and the resonance fields shifted as the temperature was decreased. These tendencies were suppressed as the Cr 3+ concentration was decreased. The ESR results were compared with those of another frustrated magnet and mechanism of the resonance field shift was discussed.

High Field ESR Study of theS=1/2 Diamond-Chain Substance Cu3(CO3)2(OH)2up to the Magnetization Plateau Region

“…12) Although the magnetization measurement of Cu 3 (CO 3 ) 2 (OH) 2 at 4.2 K showed a monotonical increase up to 26 T and then an abrupt increase up to the saturation at 32.5 T, 7) the 1/3 magnetization plateau in the magnetic field region between 16 and 26 T has been observed recently for H k b at 1.5 and 2.1 K. 12) These results seem to suggest that the ground state of Cu 3 (CO 3 ) 2 (OH) 2 at low field is in the SF phase (dimer-monomer phase). The magnetic nature of the 1/3 magnetization plateau is still an interesting subject.…”

“…7) Therefore, we speculate that the appearance of the new resonance B for H k b below 8.9 K and the second maximum around 5 K in the magnetic susceptibility 12) is due to the formation of a singlet dimer in the SF state.…”

“…5 K 12) suggesting that the system is gapless. Then the system is more likely in the SF state from the monotonical increase in the magnetization 12) and the estimation J 2 =J 1 > 2 from the magnetic susceptibility analysis.…”