Journal of the Physical Society of Japan · 1997 · 97 citations · 11 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsMagnetic MaterialsPhysical ChemistryAntiferromagnetismExchange InteractionsFerromagnetic MaterialsFerromagnetismMagnetic Properties Of SolidsMagnetic SusceptibilityAntiferromagnetic ExchangeAntiferromagnetic OrderExchange Interactions In Heisenberg ModelsHeisenberg MagnetismMagnetic Properties Of Transition Metal ComplexesMagnetism Of Transition Metal ComplexesSuperexchangeSuperexchange Mechanism
On measuring the dependence of the magnetic susceptibility of (CH 3 ) 2 CHNH 3 CuCl 3 on the temperature, we find that this compound forms ferromagnetic and antiferromagnetic alternating linear chains with S =1/2. The magnetic susceptibilities observed in external fields applied along three different surfaces of an as-grown single-crystal sample show broad peaks at around 24 K and steeply decrease to zero with further decreases in temperature toward 0 K. Two types of superexchange interactions defined in the Hamiltonian H = -2 J 1 ∑ S 2 i · S 2 i +1 - 2 J 2 ∑ S 2 i · S 2 i -1 are determined to be J 1 / k =-23.5 K and J 2 / k =+54.1 K, which indicates that a pair of ferromagnetically coupled spins behaves as a spin of S =1 and thus this compound is regarded as antiferromagnetic linear chains with S =1. The present system can therefore be discussed in terms of the Haldane conjecture for integer spins. The energy gap is estimated to be 17.1∼18.1 K.
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