Temperature dependence of the effective anisotropy in Ni nanowire arrays

MENESES, FERNANDO; URRETA, SILVIA E.; ESCRIG, JUAN; BERCOFF, PAULA G.

CURRENT APPLIED PHYSICS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

1567-1739

Magnetic hysteresis in Ni nanowire arrays, grown by electrodepositioninside the pores of anodic alumina templates, is studied as a function oftemperature in the range 5K-300K. Nanowires with different diameters, aspectratios, inter-wire distance in the array and surface condition (smooth andrough) are synthesized. These microstructural parameters are linked to the differentfree magnetic energy contributions determining the coercivity value and themagnetization reversal controlling mechanisms. The temperature dependent magnetic behavior isdescribed in terms of an effective magnetic anisotropy Ka, resulting from the interplay of magnetocrystalline, magnetoelastic andshape anisotropies, together with the magnetostatic interaction energy density betweennanowires in the array. Micromagnetic calculations of the coercive fieldallowed predicting, on the basis of microstructural parameters, themagnetization reversal mode in each studied array. From these data, theeffective anisotropy Ka could be estimated, giving positive or negativevalues for samples with 200nm and 33nm diameters, respectively, along thetemperature range. Nanowires of 65nm diameter exhibit negative values of Kabelow 150K and positive ones above this temperature. A method is proposed toroughly estimate the value of Ka experimentallyfrom the hysteresis loops measured at different temperatures. These measuredvalues are in agreement with theoretical calculations.