Effects of transition metal doping on multiferroic ordering in ni3v2o8 and fevo4
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EFFECTS OF TRANSITION METAL DOPING ONMULTIFERROIC ORDERING INNi3V2O8 ANDFeVO4byAKILA KUMARASIRIDecember 2012Advisor : Dr. Gavin LawesMajor : PhysicsDegree : Doctor of PhilosophyWe have studied the effects of doping both non-magnetic and magnetic ions on the phasetransitions and multiferroic ordering in two multiferroic oxides; Ni3V2O8 and FeVO4. Magnetic,dielectric, specific heat, polarization and AC susceptibility measurements were used to trackchanges in phase transition temperatures. We found that the two higher temperature magnetictransitions in Ni3V2O8; TH = 9.1 K and TL = 6.3 K are suppressed to lower temperatures with alltransition metal dopants. For Zn doping, the rates of the suppression of both TH and TL withdopant fraction are consistent with simple site dilution for two-dimensional spin systems, withthe suppression of TH consistent with Ising spins and the suppression of TL consistent withHeisenberg spins. However, samples remain multiferroic at least up to 15% Zn doping.Conversely, spin-1/2 Cu doping strongly suppresses both transitions, for which the multiferroic
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