Spin-specific heat determination of the ratio of competing first- and second-neighbor exchange interactions in frustrated spin-1/2 chains

摘要

Themagnetic susceptibility chi(T) of spin-1/2 chains is widely used to quantify exchange interactions, even though chi(T) is similar for different combinations of ferromagnetic J(1) between first neighbors and antiferromagnetic J(2) between second neighbors. We point out that the spin-specific heat C(T) directly determines the ratio alpha = J(2)/vertical bar J(1)vertical bar of competing interactions. The J(1)-J(2) model is used to fit the isothermal magnetization M(T, H) and C(T, H) of spin-1/2 Cu(II) chains in LiCuSbO4. By fixing alpha, C(T) resolves the offsetting J(1), alpha combinations obtained from M(T, H) in cuprates with frustrated spin chains.