M. K. Chattopadhyay

Large inverse magnetocaloric effect in Ni50Mn34In16

We report a study of the magnetocaloric effect in the ternary alloy system Ni50Mn34In16. This system undergoes an austenite–martensite phase transition, and the change in magnetic entropy is found to be quite large across this martensitic transition. This entropy change is due to an increase in entropy induced by the application of an external magnetic field and can lead to a large inverse magnetocaloric effect. Isothermal magnetic field variation of magnetization exhibits field hysteresis in Ni50Mn34In16 across the martensitic transition. But in spite of the hysteresis losses, a large effective refrigerant capacity can be obtained in this material over a wide temperature interval.

Magnetocaloric effect in Heusler alloys Ni50Mn34In16 and Ni50Mn34Sn16

We present results of detailed ac susceptibility, magnetization and specific heat measurements in Heusler alloys Ni50Mn34In16 and Ni50Mn34Sn16. These alloys undergo a paramagnetic to ferromagnetic transition around 305 K, which is followed by a martensitic transition in the temperature regime around 220 K. Inside the martensite phase both the alloys show signatures of field-induced transition from martensite to austenite phase. Both field- and temperature-induced martensite–austenite transitions are relatively sharp in Ni50Mn34In16. We estimate the isothermal magnetic entropy change and adiabatic temperature change across the various phase transitions in these alloys and investigate the possible influence of these transitions on the estimated magnetocaloric effect. The sharp martensitic transition in Ni50Mn34In16 gives rise to a comparatively large inverse magnetocaloric effect across this transition. On the other hand the magnitudes of the conventional magnetocaloric effect associated with the paramagnetic to ferromagnetic transition are quite comparable in these alloys.

Kinetic arrest of the first-order ferromagnetic-to-antiferromagnetic transition in Ce ( Fe 0.96 Ru 0.04 ) 2 : Formation of a magnetic glass

We present the results of a dc magnetization and magnetic relaxation study showing the kinetic arrest of a first-order ferromagnetic-to-antiferromagnetic transition in

First-order transition from antiferromagnetism to ferromagnetism inCe(Fe0.96Al0.04)2

\mathrm{Ce}{({\mathrm{Fe}}_{0.96}{\mathrm{Ru}}_{0.04})}_{2}

Reducing the operational magnetic field in the prototype magnetocaloric system Gd5Ge4 by approaching the single cluster size limit

, resulting from the viscous retardation of growth of the antiferromagnetic phase. This leads to the formation of a nonergodic glasslike magnetic state. The onset of the magnetic-glass transformation is tracked through the slowing down of the magnetization dynamics. This glassy state is formed with the assistance of an external magnetic field and this is distinctly different from the well-known spin-glass state.

The effect of substitution of Mn by Fe and Cr on the martensitic transition in the Ni50Mn34In16 alloy

Results of dc magnetization study are presented showing interesting thermomagnetic history effects across the antiferromagnetic to ferromagnetic transition in Ce(Fe

Temperature and magnetic field induced strain in Ni50Mn34In16 alloy

_{0.96}

Thermomagnetic history dependence of magnetocaloric effect in Ni50Mn34In16

Al

Elevating the temperature regime of the large magnetocaloric effect in a Ni–Mn–In alloy towards room temperature

_{0.04})_2

Sharp magnetization step across the ferromagnetic-to-antiferromagnetic transition in doped CeFe 2 alloys

. Specifically, we observe (i)ZFC/FC irreversibility rising with increasing field; (ii) virgin curve lying outside the envelope M-H curve. We argue that these effects are quite different from the characteristics seen in spin-glasses or in hard ferromagnets; they can be understood as metastabilities associated with a first order magnetic phase transition.