Distributed exchange interactions and temperature dependent magnetization in amorphous Fe88−xCoxZr7B4Cu1 alloys

Gallagher, Kathleen; Willard, M. A.; Zabenkin, V. N.; Laughlin, David E.; McHenry, M. E.

doi:10.1063/1.369100

Cited by 86 publications

(45 citation statements)

References 13 publications

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“…These, in turn, set the scale for T C am . However, from the shape of the Bethe-Slater curve and the relative positions of Fe and Co on the curve it can be inferred that T C am of Co-based alloys is relatively invariant to disorder compared with Fe-based alloys, 17 and thus one may conclude that the observed increase of T C am with the milling time is not correlated to changes in the short-range order of the amorphous phase. As concluded from XRD observations, bcc-Fe nanocrystalline grains are formed during milling.…”

Section: Discussionmentioning

confidence: 91%

Mechanically induced crystallization of an amorphous CoFeZrB alloy

Bednarčı́k

Burkel

Saksl

et al. 2006

Journal of Applied Physics

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The short-time ͑12 h͒ ball milling of the amorphous Co 56 Fe 16 Zr 8 B 20 ͑at. %͒ alloy resulted in the formation of bcc-Fe nanocrystals embedded in an amorphous matrix. X-ray diffraction ͑XRD͒ using synchrotron radiation, differential scanning calorimetry ͑DSC͒, vibrating sample magnetometery ͑VSM͒, and the Faraday magnetic balance experiments were used to characterize the materials. XRD and DSC show that the fraction of crystallized bcc-Fe gradually increases with the milling time. The VSM measurements confirm the structure observations showing that the saturation magnetization increases with the milling time as the fraction of crystallized bcc-Fe increases. After 12 h of milling, the powder sample exhibited a Curie temperature of the amorphous phase T C am , which is approximately 55 K higher compared to the as-quenched ribbon ͑T C am = 601 K͒. Thermomagnetic measurements of heat-treated ribbons suggest that such an increase in T C am is not only due to temperature rises during the milling but may also be attributed to the combination of mechanical and thermal effects connected with the nature of milling.

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Section: Discussionmentioning

confidence: 91%

Mechanically induced crystallization of an amorphous CoFeZrB alloy

Bednarčı́k

Burkel

Saksl

et al. 2006

Journal of Applied Physics

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“…It is worth mentioning that not only changes in the atom species affect the interaction strength but also changes in the interatomic distances in the disordered structure, especially in Fe-rich FeCo-based amorphous alloys. This has been successfully modelled taking asymmetric distribution of exchange interactions by Gallagher et al [30]. The hysteresis loops for both the as-quenched and nanocrystalline alloys present the typical shape of a soft magnetic material.…”

Section: Magnetic Characterizationmentioning

confidence: 99%

Effect of minor Co additions on the crystallization and magnetic properties of Fe(Co)NbBCu alloys

Torrens‐Serra

Bruna

Roth

et al. 2010

Journal of Alloys and Compounds

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The effect of partial replacement of Fe by Co (up to 8 %) on thermal stability, structure and magnetic properties of FeNbBCu alloys has been explored in this paper. The results indicate that Co reduces the stability against crystallization of the amorphous alloy and stabilizes the nanocrystalline phase prior to the further precipitation of metastable boride phases.Transmission Mössbauer spectroscopy reveals differences in the hyperfine interactions between the alloys: Co raises the mean hyperfine field of the amorphous state and differences in the nanocrystalline bcc-Fe(Co) environments between the alloys occur depending on the amount of Co near-neighbours in the bcc-Fe structure. The addition of Co has also a notable effect on the magnetic properties of both amorphous and nanocrystalline alloys increasing the Curie temperature, which shows a linear dependence with the Co composition, and the saturation polarization.

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“…3 Additionally, this equation of state helps us understand the extra broadening in DS M resulting from the amorphous phase of the nanocomposites. According to the Bethe-Slater curve, 4,5 fluctuations in atomic spacing, as well as other disorder at defects and interfaces can lead to an asymmetric dependence of the exchange interactions.…”

Section: Introductionmentioning

confidence: 99%

The effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials

Jones¹,

Ucar²,

Ipus³

et al. 2012

Journal of Applied Physics

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The temperature dependent magnetization of nanocomposite alloys has been fit with a modified Handrich-Kobe equation with an asymmetric exchange fluctuation parameter combined with the Arrott-Noakes equation. The two equations of state are combined to calculate the entropy change in the magnetocaloric effect associated with the ferromagnetic to paramagnetic phase transformation. The complete fit for the M(T) of (Fe 70 Ni 30 ) 88 Zr 7 B 4 Cu nanocomposite powder is accomplished by combining the two theories. We investigate the broadening of the second-order transition arising from asymmetric exchange parameters and resulting from the fluctuations of interatomic spacing found in an amorphous matrix and the asymmetric dependence of exchange energy on interatomic spacing. The magnetic entropy curve revealed extra broadening with a refrigeration capacity (RC) value of 135 J/kg at 5 T, which is comparable to (Fe 76 Cr 8-x Mo x Cu 1 B 15 ) ribbons, which have a RC value of 180 J/kg for the same applied field. Broadening of the magnetic entropy can lead to larger RC values and a wider working temperature range, making nanocomposite alloys promising for magnetocaloric applications.

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Distributed exchange interactions and temperature dependent magnetization in amorphous Fe88−xCoxZr7B4Cu1 alloys

Cited by 86 publications

References 13 publications

Mechanically induced crystallization of an amorphous CoFeZrB alloy

Mechanically induced crystallization of an amorphous CoFeZrB alloy

Effect of minor Co additions on the crystallization and magnetic properties of Fe(Co)NbBCu alloys

The effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials

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