Relationship between coercivity and magnetic moment of superparamagnetic particles with dipolar interaction

Blázquez

et al. 2006

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118

mentioning

confidence: 98%

A Finemet-type alloy as a low-cost candidate for high-temperature magnetic refrigeration

Blázquez

et al. 2006

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118

“…This approach is analogous to previous phenomenological models applied to completely different complex phenomena, like the superparamagnetic transition of dipolarly interacting superparamagnetic particles, in which an effective temperature, related to the energy of magnetic dipolar interactions, was introduced to reproduce the temperature dependence of the hysteretic behavior. [11][12][13] It is worth noticing that the definition of T* introduced in expression (4) has no free parameter and depends only on the two excitations involved (field and temperature) and on the properties of the material (magnetic moment and entropy change of the transition). The former property, as described above, has been obtained from fitting the magnetization of the pure austenite phase, while DS tr will be obtained from the field dependence of the transition, as will be shown below.…”

mentioning

confidence: 99%

A unified approach to describe the thermal and magnetic hysteresis in Heusler alloys

Blázquez

et al. 2016

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Different excitations, like temperature, magnetic field, or pressure, can drive a martensitic transition in Heusler alloys. Coupled phenomena in these materials lead to interesting magnetocaloric and barocaloric effects ascribed to this transition. In this work, we demonstrate that isothermal transformations induced by a magnetic field and isofield transformations induced by the temperature can be described using the same framework. By defining an effective temperature that relates field and temperature through the properties of the system (magnetic moment and entropy of the transition), both kinds of loops can be transformed into the other kind, therefore providing a more effective way of characterizing hysteretic samples. The validity of this effective temperature approach to describe the transition holds for martensite to austenite transformations as well as reversal ones, and thus, the hysteresis phenomena can be described using this single general excitatio

“…Although both alloying elements produce a similar reduction in the Curie temperature of the amorphous alloy, displacing it to temperatures closer to room temperature, [24][25][26] it has been recently shown that the combined addition of Cr and Mo to a Nanoperm alloy has an increased efficiency in reducing T Curie with respect to the Mo-free alloy. 27 Therefore, the purpose of this letter is to analyze the influence of Cr and Cr/ Mo addition on the magnetocaloric effect of a Nanoperm-type amorphous alloy. It will be shown that both RC and ͉⌬S M pk ͉ are reduced for the Mo-containing alloy, although the RC values presented in this letter are higher than those of other Nanoperm-type amorphous alloys, making the studied samples promising candidates for magnetic refrigerants.…”

mentioning

confidence: 99%

Enhanced magnetocaloric response in Cr∕Mo containing Nanoperm-type amorphous alloys

et al. 2007

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The magnetocaloric effect of Fe76Cr8−xMoxCu1B15 (x=0,4) alloys is studied. Although the combined addition of Cr and Mo is more efficient in tuning the Curie temperature of the alloy, the Mo-free alloy presents a higher magnetocaloric response. The refrigerant capacity (RC) for the Mo-containing alloy is comparable to that of Gd5Ge1.9Si2Fe0.1 (for a field of 50kOe, RC=273Jkg−1 for the Mo alloy vs 240Jkg−1 for the Gd-based one), with a larger temperature span of the optimal refrigeration cycle (250K vs 90K, respectively). The restriction of the temperature span to 90K gives RC=187Jkg−1 for the Mo alloy. A master curve behavior for the magnetic entropy change is also evidenced.