Structural and Magnetic Properties of MnFe$_1 - rm x$Co$_rm x$Ge Compounds

Lin, Shuichao; Tegus, O.; Brück, E.; Dagula, W.; Gortenmulder, T.J.; Buschow, K.H.J.

doi:10.1109/tmag.2006.884516

Cited by 108 publications

(51 citation statements)

References 9 publications

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“…The implication is therefore that the useful refrigerant capacity of such a magnetostructrual phase transition is much lower than it might appear from a single entropy curve such as that presented in Figure 4. For a magnetic refrigerant, it is therefore more attractive to keep the structural and magnetic transitions close in temperature, but not overlapping, as was attained by Koyama et al and Lin et al [14,24]. Proximity of the first order structural transition can tend to sharpen the continuous magnetic transition, and improve the entropic response, without invoking large magnetic or thermal hysteresis.…”

Section: Magnetic Measurementsmentioning

confidence: 99%

Phase diagram and magnetocaloric effect ofCoMnGe1-xSnxalloys

Hamer

Daou

Özcan

et al. 2009

Journal of Magnetism and Magnetic Materials

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We propose the phase diagram of a new pseudo-ternary compound, CoMnGe 1−x Sn x , in the range x≤0.1. Our phase diagram is a result of magnetic and calometric measurements. We demonstrate the appearance of a hysteretic magnetostructural phase transition in the range x = 0.04 to x = 0.055, similar to that observed in CoMnGe under hydrostatic pressure. From magnetisation measurements, we show that the isothermal entropy change associated with the magnetostructural transition can be as high as 4.5 JK −1 kg −1 in a field of 1 Tesla. However, the large thermal hysteresis in this transition (∼20 K) will limit its straightforward use in a magnetocaloric device.

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Section: Magnetic Measurementsmentioning

confidence: 99%

Phase diagram and magnetocaloric effect ofCoMnGe1-xSnxalloys

Hamer

Daou

Özcan

et al. 2009

Journal of Magnetism and Magnetic Materials

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“…As the first generation of magnetocalorics moves towards commercial viability, more and more diverse applications of the magnetocaloric effect are being proposed, including gas liquefaction, 12 small-scale solid state cooling, 13 and thermomagnetic generators. 14 These applications will each demand materials with different properties, including a range of active temperatures, cycling properties, thermal properties, and magnetic field responses.…”

Section: Introductionmentioning

confidence: 99%

A Simple Computational Proxy for Screening Magnetocaloric Compounds

et al. 2017

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Alternating cycles of isothermal magnetization and adiabatic demagnetization applied to a magnetocaloric material can drive refrigeration in very much the same manner as cycles of gas compression and expansion. The material property of interest in finding candidate magnetocaloric materials is their gravimetric entropy change upon application of a magnetic field under isothermal conditions. There is, however, no general method of screening materials for such an entropy change without actually carrying out the relevant, time-and effort-intensive magnetic measurements. Here we propose a simple computational proxy based on carrying out non-magnetic and magnetic density functional theory calculations on magnetic materials. This proxy, which we refer to as the magnetic deformation Σ M , is a measure of how much the unit cell deforms when comparing the relaxed structures with and without the inclusion of spin polarization. Σ M appears to correlate very well with experimentally measured magnetic entropy change values. The proxy has been tested against 33 known ferromagnetic materials, including nine materials newly measured for this study. It has then been used to screen 134 ferromagnetic materials for which the magnetic entropyhas not yet been reported, identifying 30 compounds as being promising for further study. As a demonstration of the effectiveness of our approach, we have prepared one of these compounds and measured its isothermal entropy change. MnCoP, with T C = 575 K, shows a maximum ∆S M = −6.0 J kg −1 K −1 for an applied field of H = 5 T.2

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“…10,11 The magnetic and crystallographic transitions can be coupled in many ways. We have recently reported that the addition of B as an interstitial and the substitution of Cr on the MnCoGe lattice can be used to make the magnetic and structural phase transitions coincide, giving rise to a giant magnetocaloric effect.…”

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confidence: 99%

Pressure-tuned magnetocaloric effect in Mn0.93Cr0.07CoGe

2011

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Effects of physical and chemical pressures in the Mn 1−x Cr x CoGe series of compounds are studied. Cr substitution and hydrostatic pressure play similar roles in displacing T C to lower temperatures and coupling or decoupling magnetic and crystallographic transitions. In this work the similarities and differences between the effects of chemical and physical pressures are explored, helping unveil the nature of the first-order phase transition presented by MnCoGe-based compounds. DOI: 10.1103/PhysRevB.84.020414 PACS number(s): 75.30.Cr, 75.30.Sg, 75.50.Cc, 75.80.+q Since the discovery of the giant magnetocaloric effect on FeRh 1 and the subsequent observation of a tunable giant entropy change ( S M ) on Gd 5 Ge 2 Si 2 , 2 magnetic refrigeration based on the magnetocaloric effect has gained increasing attention. It is regarded as a promising, more efficient, and environmentally friendly alternative to gas-compression-based refrigeration due to its potential applications in a wide range of temperatures.Materials presenting first-order magnetic phase transitions are of special interest since they intrinsically present high S M originating from the discontinuous character of the transition. These transitions can be observed in a series of low-cost 3d metal-based compounds such as MnAs,Ni 0.5 Mn 0.5 Sn, 5 and (Mn,Fe) 2 (P,As) 1 . 6 Such transitions are always accompanied by a discontinuous change in the lattice parameters and often in volume, but do not always result in a crystal symmetry change. Materials presenting only lattice parameters and/or volume change around the phase transition are said to undergo a magnetoelastic phase transition, e.g., all Fe 2 P-based compounds as well as La(Fe,Si) 13 , 7 while those which also show a change in crystal structure undergo a magnetostructural phase transition, e.g., FeRh, Gd 5 Ge 2 Si 2 , MnAs, and Ni 0.5 Mn 0.5 Sn.Since magnetic interactions are sensitive to interatomic distances, chemical pressure-substitutions, dopings, and interstitial elements-has been largely used to tune magnetic properties. Both magnetic and crystallographic phasetransition temperatures can be tuned using chemical pressure. This allows for first-order phase-transition temperatures to be easily tuned. But, more importantly, it allows for chemical pressure to be used to simultaneously tune separate magnetic and crystallographic transitions to coincide, giving rise to coupled first-order transitions. Thus, chemical pressure is an invaluable tool not only to tune but also to create magnetoelastic and magnetostructural couplings. A good example of both the creation and tuning of a magnetostructural coupling comes from the MnCoGe system.MnCoGe is a 3d metal-based ferromagnet with a Curie temperature (T C ) of ∼345 K and a diffusionless crystallographic phase transition from the low-temperature orthorhombic TiNiSi type to the high-temperature hexagonal Ni 2 In type of structure at ∼650 K. 8,9 In both orthorhombic and hexagonal structures it behaves as a typical ferromagnet with second-order phase trans...

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Structural and Magnetic Properties of MnFe$_1 - rm x$Co$_rm x$Ge Compounds

Cited by 108 publications

References 9 publications

Phase diagram and magnetocaloric effect ofCoMnGe1-xSnxalloys

Phase diagram and magnetocaloric effect ofCoMnGe1-xSnxalloys

A Simple Computational Proxy for Screening Magnetocaloric Compounds

Pressure-tuned magnetocaloric effect in Mn0.93Cr0.07CoGe

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