Abstract :
We have studied the electronic structure of the molecular ferromagnet β -Mn phthalocyanine ( β -MnPc) in a polycrystalline form, which has been reported to show ferromagnetism at T < 8.6 K , by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). From the experimental results and subsequent cluster-model calculation, we find that the ferromagnetic Mn ion in β -MnPc is largely in the 4 E g ground state arising from the ( e g ) 3 ( b 2 g ) 1 ( a 1 g ) 1 [ ( d x z , y z ) 3 ( d x y ) 1 ( d z 2 ) 1 ] configuration of the Mn2+ state. Considering that the highest occupied molecular orbital (HOMO) of MnPc with the 4 E g ground state originates from the a 1 g orbital of the Mn2+ ion, it is proposed that a 1 g – a 1 g exchange coupling via the π orbitals of the phthalocyanine ring plays a crucial role in the ferromagnetism of β -MnPc.
