CoFe–Cu granular alloys: From noninteracting particles to magnetic percolation
نویسندگان
چکیده
CoFe–Cu granular films with ferromagnetic content ranging from 0.10 to 0.33 by volume were prepared by radio frequency sputtering. As-cast samples were rapidly annealed at various temperatures up to 750 °C to promote the segregation of CoFe particles within the metallic matrix. Magnetic and transport properties suggested that this family of samples may be classified into three groups: ~i! below about 0.20 volume content of CoFe, all samples display the typical features of a granular solid constituted by a random distribution of nanometric CoFe particles within a Cu matrix, and the maximum magnetoresistance is about 20% at low temperature ~giant magnetoresistance!; ~ii! for as-cast samples within 0.20 and 0.30 of volume concentration, magnetoresistance and magnetization display complex bimodal behavior and large metastable effects associated with the interparticle interactions, which stabilize a domain-like microstructure well below the volume percolation threshold ~0.55!, as already observed in CoFe–Ag~Cu! granular alloys. As a consequence of the large magnetic correlations, magnetoresistance is very low ~1%–3%!. Through annealing, the microstructure and therefore the transport properties evolve to those of a classical giant magnetoresistance system with large particles; and ~iii! above about 0.30 of volume content ~and still below the volume percolation threshold!, as-cast samples display both anisotropic and giant magnetoresistance, as also observed in other granular alloys. Annealing leads to complete segregation and to the formation of large magnetic particles, which results in a transition from mixed behavior of both anisotropic and giant magnetoresistance ~GMR! regimes to a giant magnetoresistance regime, with a maximum GMR of about 7%. © 1999 American Institute of Physics. @S0021-8979~99!01810-1#
منابع مشابه
Remanence breakdown in granular alloys at magnetic percolation
Microstructural effects on the magnetic behavior of rf-sputtered CoFe–AgCu granular alloys are examined through the study of the in-plane remanence-to-saturation magnetization ratio, M r /M s , as a function of temperature, ferromagnetic volume content, xv , and annealing temperature. At low ferromagnetic contents (xv<0.25), the M rM s ratio in as-deposited samples tends towards 0.5 at low temp...
متن کاملMagnetic properties of an Fe/Cu granular multilayer
A Cu/Fe granular film, formed from a multilayer film and composed of particles of Fe imbedded in Cu, has had several of its important properties investigated. Measurements include ferromagentic resonance, magnetoresistance, Miissbauer effect, magnetic viscosity, and magnetization. The two-phase behavior of these immiscible alloy systems, and the effect of multilayering on the shape of the magne...
متن کاملCoFe Layers Thickness and Annealing Effect on the Magnetic Behavior of the CoFe/Cu Multilayer Nanowires
CoFe/Cu multilayer nanowires were electrodeposited into anodic aluminum oxide templates prepared by a two-step mild anodization method, using the single-bath technique. Nanowires with 30 nm diameter and the definite lengths were obtained. The effect of CoFe layers thickness and annealing on the magnetic behavior of the multilayer nanowires was investigated. The layers thickness was controlled t...
متن کاملDevelopment of Novel Prototype Scalable Magnetoresistive Random Access Memory
MRAM has received a great deal of attention in recent years for its potential to become a universal memory capable of nonvolatility, infinite cycleability, fast switching speeds, high density, and low cost. However, the limitations of conventional design architectures have made MRAM difficult to realize. In this work, a new annular currentperpendicular-to-plane (CPP) giant magnetoresistive (GMR...
متن کاملCritical Parameters of Solution Design for Electrodeposition of 2.4 T CoFe Alloys
The electrodeposition of soft, high magnetic moment alloys has become the critical fabrication step in manufacturing of magnetic recording heads. The need for ultimately high magnetic moment alloys (2.4 T CoFe) and the electrodeposition process capable of delivering magnetic structures with dimension in the range of several tens of nanometers are the new tasks that have to be addressed if the f...
متن کامل