One-dimensional Quantum Magnetism Of Rare Earth Perovskite YbM?M=Al,Cr?O₃

The perovskite material with the chemical composition ABO₃ has attracted great attention.Due to the diversity of its structural deformation and M-site metal ions,as well as various microscopic interactions and delicate balances between electrons,spins,orbits,charges and lattice freedom,we can observe a variety of novel physical phenomenon.The rare earth perovskite has many interesting magnetic phenomena,such as multiferroicity,spin reorientation,and quantum critical phenomena,because of the coupling between the 4f and 3d sublattices.Therefore,this dissertation systematically studied the rare earth perovskite Yb M?Al,Cr?O₃ system,and explored their magnetic properties as well as quantum critical phenomena.YbAlO₃ is a one-dimensional quantum magnet,and its strong quantum fluctuations have caused many novel phenomena.By exploring the magnetocaloric effect of YbAlO₃,the phase diagram of YbAlO₃ at low temperature was depicted more clearly.In addition,the 1/3 and 1/2 quantized plateaus in the IC-antiferromagnetic phase near the quantum critical point was observed.The discovery of these quantized platforms has a very important significance for future theoretical development and the interpretation of quantum critical phenomena in low-dimensional quantum magnets.By replacing nonmagnetic Al³⁺with magnetic Cr³⁺,we studied the crystal growth and low-temperature magnetism of Yb Cr O₃.A high-quality single crystal sample was grown by the flux method.Neutron scattering experiments were performed,and the magnetic structure of Yb Cr O₃ is determined to be Fx Cy Gz-type.The powder neutron diffraction measurements inditate that Yb³⁺and Cr³⁺are antiferromagnetically coupledas previously reported.However,the refined ordered moment of Yb site is very small,suggesting that most of the Yb moments are not fully polariezed.The magnetization and specific heat of Yb Cr O₃ were systematically studied as well.Negative magnetization was observed at low temperatures,which is consistent with the expectation that Yb and Cr sites are antiferromagnetically coupled.