Impurity Spin Resonance in Antiferromagnetic CoCl₂2H₂O

Abstract

Electron spin resonance of Mn²⁺ ions in antiferromagnetic CoCl₂2H₂O was investigated using microwaves and pulsed magnetic fields. The results indicate that the Mn²⁺ ion couples with surrounding Co spins by relatively weak exchange interactions and the effective spin Hamiltonian can be written by
H=g₀μ_B(H₀+H_E)S₀+DS_0z²,
where the first term represents the Zeeman energy of the impurity spin S₀ under an external magnetic field H₀ and the resultant effective field H_E coming from the neighboring Co spins. By analyzing the experimental results, three exchange constants J₀′, J₁′ and J₂′ are obtained as J₀′(F)=0.59±0.04 cm⁻¹, J₁′(AF)=0.73±0.02 cm⁻¹ and J₂′(AF)=0.23±0.03 cm⁻¹, where F and AF mean the ferromagnetic and antiferromagnetic coupling, respectively. D was determined to be −0.13±0.01 cm⁻¹.