Journal ArticleDOI
Magnetic phase transitions and the magnetothermal properties of gadolinium
TLDR
A study of four Gd samples of different purities using ac susceptibility, magnetization, heat capacity, and direct measurements of the magnetocaloric effect in quasistatic and pulse magnetic fields revealed that all techniques yield the same value of the zero-field Curie temperature of 294(1) K as mentioned in this paper.Abstract:
A study of four Gd samples of different purities using ac susceptibility, magnetization, heat capacity, and direct measurements of the magnetocaloric effect in quasistatic and pulse magnetic fields revealed that all techniques yield the same value of the zero-field Curie temperature of 294(1) K. The Curie temperature determined from inflection points of the experimental magnetic susceptibility and heat capacity is in excellent agreement with those obtained from the magnetocaloric effect and Arrot plots. Above 2 T the temperature of this transition increases almost linearly with the magnetic field at a rate of $\ensuremath{\sim}6\mathrm{K}/\mathrm{T}$ in fields up to 7.5 T. The spin reorientation transition, which occurs at 227(2) K in the absence of a magnetic field, has been confirmed by susceptibility, magnetization, and heat-capacity measurements. Magnetic fields higher than 2--2.5 T apparently quench the spin reorientation transition and Gd retains its simple ferromagnetic structure from the ${T}_{C}(H)$ down to $\ensuremath{\sim}4\mathrm{K}.$ The nature of anomaly at $T\ensuremath{\cong}132\mathrm{K},$ which is apparent from ac susceptibility measurements along the $c$ axis, is discussed. The presence of large amounts of interstitial impurities lowers the second-order $\mathrm{paramagnetic}\ensuremath{\leftrightarrow}\mathrm{ferromagnetic}$ transition temperature, and can cause some erroneous results in the magnetocaloric effect determined in pulsed magnetic fields. The magnetocaloric effect was studied utilizing the same samples by three experimental techniques: direct measurements of the adiabatic temperature rise, magnetization, and heat capacity. All three techniques, with one exception, yield the same results within the limits of experimental error.read more
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Journal ArticleDOI
Tuning magnetocaloric effect with nanocrystallite size
S. P. Mathew,S. N. Kaul +1 more
TL;DR: In this article, the average nanocrystallite size and size distribution can be used as control parameters to respectively tune the peak value and the width at half-maximum of the isothermal magnetic entropy change or the adiabatic temperature change during the magnetization process.
Journal ArticleDOI
Sensitivity study of multi-layer active magnetic regenerators using first order magnetocaloric material La(Fe,Mn,Si)13Hy
Tian Lei,Kaspar Kirstein Nielsen,Kurt Engelbrecht,Christian R.H. Bahl,Henrique Neves Bez,Christian Veje +5 more
TL;DR: In this paper, the authors present simulation results of multi-layer active magnetic regenerators using the solid-state refrigerant La(Fe,Mn,Si)13Hy.
Journal ArticleDOI
Large room-temperature magnetocaloric effects in Fe0.8Mn1.5As
TL;DR: In this article, the sign of the entropy change ΔSM in the compound is unexpectedly negative, revealing a different mechanism, and the maximum value of ΔSM is 6.2J∕kgK at 287.5K for a magnetic field change of 5T.
Journal ArticleDOI
Development of an experimental rotary magnetic refrigerator prototype
Bowei Huang,Bowei Huang,Jiawei Lai,Jiawei Lai,Dechang Zeng,Z.G. Zheng,B. Harrison,A. Oort,N.H. van Dijk,Ekkes Brück +9 more
TL;DR: In this article, a rotary active magnetic regeneration refrigerator prototype named FAME Cooler was developed for studying the performance of different magnetocaloric materials in a realistic practical environment, which achieved a maximum zero-span cooling power of 162.4 W, and a zero-power temperature span of 11.6
Journal ArticleDOI
Enhancement of magnetocaloric effects in La1−zPrz(Fe0.88Si0.12)13 and their hydrides
TL;DR: In this article, the magnetocaloric effects in La1−zPrz(Fe0.88Si0.12)13 and their hydrides have been investigated and the values of the MCE due to the itinerant-electron metamagnetic transition are enhanced significantly by a partial substitution of Pr for La.