Magnetic Study of Dilute Magnetic Glasses: [40B2O3+30Na2O+(30-x)V2O5+xFe2O3] with x=0 to 5

P. Chand, L. Kumar Materials Science, Department of Physics, SRM University, Delhi-NCR Sonepat-131029, Haryana, India

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A magnetic study of dilute magnetic glasses 40B2O3+30Na2O+(30-x)V2O5+xFe2O3 with x=0, ... ,5 (abbreviated as FVNBx) has been undertaken to understand the effect of magnetic interactions and super-exchange between like and unlike spins. Two complementary experimental techniques were used, namely, the magnetization measurement and the EPR spectroscopy. The study confirmed a minor presence of an active V4+ oxidation state in the form of a vanadyl (V=O)2+ molecular ion. The majority of vanadium remains in the diamagnetic V5+ oxidation state. It is apparent that vanadium contributes little to the magnetization of these glasses. The experimental value of magnetization of FVNB0 was used to evaluate the concentration of V4+ and it was found that only 11% of total vanadium transforms to the magnetic V4+ oxidation state. The magnetization attributed to iron was found also reduced by an order of magnitude from the expected value. The canted antiferromagnetic pairing of the magnetic dipoles is suggested to cause the reduction in the observed magnetization. The effects of magnetic interactions (both dipolar as well as super-exchange) are clearly observed in the EPR spectra of both V4+ and Fe3+ in these glasses. The observed features of EPR are the evidence that iron is experiencing highly distorted oxygen environments (octahedral/tetragonal/tetrahedral) in these glasses, resulting in very high zero field splitting D for the local Fe3+ sites. The large D and magnetic exchange interactions between the like and unlike spins are responsible for the complex features of the EPR spectra.

DOI:10.12693/APhysPolA.140.145 topics: EPR, dilute magnetic glasses, magnetization, iron