Co-rich cobalt platinum nanowire arrays: Effects of annealing

Abstract

The effects of annealing on the crystal structure and magnetic properties of Co-rich cobalt platinum nanowire arrays embedded in anodic aluminium oxide membranes have been investigated. For this purpose, a rapid thermal annealing to temperatures of 300°C to 800°C has been used. Transmission electron microscopy and scanning electron microscopy show that the nanowires have a mean diameter of 14 nm and an estimated wire density of 7.8ϫ 10 10 cm −2 . From x-ray diffraction patterns, we find that the nanowires are hcp and possess a preferred texture in which the c axis of the grains tends to lie along the major axis of the wire. Vibrating sample magnetometry measurements indicate that the easy axis is along the nanowire axis direction. Hysteresis loops, saturation magnetization, squareness ratio ͑M r / M s ͒, and coercivity ͑perpendicular and parallel to the nanowire axis͒ have all been investigated as a function of the annealing temperature ͑T A ͒. Coercivity parallel to the wire axis first increases with T A , attains a maximum at 600°C ͑which is 150% of the as-deposited sample͒, and then decreases. By contrast there is relatively little change in the coercivity measured perpendicular to the wires. The saturation magnetization for the as-deposited sample is 1360 emu/ cc and remains almost constant for annealing temperatures up to 500°C: for T A Ͼ 500°C it decreases significantly. The maximum ͑M r / M s ͒ ratio attained in this study is 0.99, the highest value reported thus far for cobalt platinum alloy nanowires. The data suggest that these materials are potential candidates for high-density magnetic recording media.

Magnetic nanowires fabricated by anodic aluminum oxide template—a brief review

“…To characterize the dimensions, morphology and crystalline structures of the AAO template and the nanowires, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) as well as X-ray diffraction (XRD) are the experimental techniques most frequently employed [30][31][32]. XRD can be carried out on as-grown samples without further specimen preparation especially when the AAO template cannot be readily removed after annealing [33].…”

Magnetic properties of Fe0.95Pd0.05 nanowire arrays

“…In fact, there are many reports on FePt and CoPt nanowires [1][2][3][4][5] as well as numerous investigations on FePd alloys utilized in bulk as well as thin film forms [6][7][8]. These binary alloys, in particular, can form a chemically ordered L10 phase that exhibits large uniaxial magnetocrystalline anisotropy.…”

A trinuclear platinum–cobalt acetate-bridged complex {PtII(acac)}2CoII(μ-OOCMe)4: Synthesis and structure

“…Traditionally these materials are produced by fusion of the component metals or reduction of mixtures of the corresponding metal salts. Alternatively, a Pt-Co alloy could be prepared from a heterobimetallic Pt II Co II carboxylate-bridged precursor, by analogy with the earlier reported [7] Pd-Zn nanoalloy obtained by easy reduction of the acetate complex Pd II (lOOCMe) 4 Zn II (OH 2 ) under mild conditions (5-10% H 2 /He, 150-250°C). However, none of the structurally characterized heterometallic Pt II -Co II carboxylate complexes have been documented so far.…”

“…Heterobimetallic platinum(II)-cobalt(II) complexes attract attention as promising precursors for platinumcobalt mixed-metal materials and alloys, which find wide use as materials for catalysis [1][2][3], high coercivity magnets [4], storing information [5] and jewelry [6]. Traditionally these materials are produced by fusion of the component metals or reduction of mixtures of the corresponding metal salts.…”

“…Herein we report the synthesis of a Pt II -Co II heterodimetallic complex {Pt II (acac)} 2 Co II (l-OOCMe) 4 (2) by the reaction of platinum(II) bis(acetylacetonate) and cobalt(II) acetate [10].…”