Bilayer exchange coupling and Neel temperature
of YBa₂Cu₃O_6.2

GOVIND, A PRATAP, AJAY and R S TRIPATHI

Department of Physics, G.B. Pant University of Agriculture and Technology, Pantnagar 263 145, India

Abstract.

The present paper attempts to study the Neel temperature of bilayer antiferromagnetic cuprate YBa₂Cu₃O_6.2 within anisotropic Heisenberg model. The double time Green's function formalism within random phase approximation (RPA) has been used to obtain various correlation functions. The magnetization and the Neel temperature (T_N) are evaluated. It is observed that the ratio of intrabilayer to inplane exchange coupling (r = J_^/J_||) plays an important role in the magnetic dynamics of bilayer systems. The recent experimental data of bilayer system YBa₂Cu₃O_6.2 have been used to estimate the ratio r from the expression for Neel temperature. The estimated values of spin gap and the ratio of hopping matrix elements t_^/t_|| are found to be in fairly good agreement with the existing experimental results.

Keywords Bilayer antiferromagnets; high-T_c superconductors; Neel temperature.

Pacs No. 75.30; 74.72 Bk; 75.10 Jm

 

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