Reversal modes in FeCoNi nanowire arrays: Correlation between magnetostatic interactions and nanowires length

Abstract

FeCoNi nanowire arrays(175nm in diameter and lengths ranging from 5 to 40 μm) were fabricated into nanopores o fhard-anodized aluminum oxide templates using pulsed ac electrodeposition technique. Increasing thelengthhadnoconsiderableeffectonthecompositionandcrystallinecharacteristicsof Fe47Co38Ni15 nanowires(NWs).Byeliminatingthedendritesformedatthebottomofthepores,we report acarefulinvestigationontheeffectofmagnetostaticinteractionsonmagneticpropertiesandthe effect ofnanowirelengthonreversalmodes.Hysteresisloopmeasurementsindicatedthatincreasingthe length decreasescoercivityandsquarenessvalues.Ontheotherhand, first-order reversalcurvemea- surements showalinearcorrelationbetweenthemagnetostaticinteractionsandlengthofNWs.Com- paring reversalmodesoftheNWsbothexperimentallyandtheoreticallyusingangulardependenceof coercivity,we find thatwhen Lr22 μm, avortexdomainwallmodeisonlyoccurred.When L422 μm, a non-monotonicbehaviorindicatesatransitionfromthevortextotransversedomainwallpropagation. As aresult,acriticallengthwasfoundabovewhichthetransitionbetweenthereversalmodesisoc- curred duetheenhancedinteractions.Thetransitionanglealsoshiftstowardalowerangleasthelength increases. Moreover,withincreasinglengthfrom22to31 μm, thesingledomainstructureofNWs changes toapseudosingledomainstate.Amultidomain-likebehaviorisalsofoundforthelongestNWs length.