Magnetic and Structural Properties of Metamagnetic MnCo0.92Fe0.08Ge Compound (original) (raw)
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Structural and magnetic properties of MnCo1−xFexSi alloys
Journal of Magnetism and Magnetic Materials, 2015
The crystal structures, martensitic structural transitions and magnetic properties of MnCo 1-x Fe x Si (0 ≤ x ≤ 0.50) alloys were studied by differential scanning calorimetry (DSC), x-ray powder diffraction (XRD) and magnetic measurements. In high-temperature paramagnetic state, the alloys undergo a martensitic structural transitions from the Ni 2 In-type hexagonal parent phase to the TiNiSi-type orthorhombic martensite. Both the martensitic transition temperature (T M) and Curie temperatures of martensite (C M) decrease with increasing Fe content. The introduced Fe atoms establish ferromagnetic (FM) coupling between Fe-Mn atoms and destroy the double spiral antiferromagnetic (AFM) coupling in MnCoSi compound, resulting in a magnetic change in the martensite phase from a spiral AFM state to a FM state. For the alloys with x = 0.10, 0.15 and 0.20, a metamagnetic transition was observed in between the two magnetic states. A magnetostructural phase diagram of MnCo 1-x Fe x Si (0 ≤ x ≤ 0.50) alloys was proposed.
Journal of Magnetism and Magnetic Materials, 2016
The thermal, structural and magnetic properties were studied for the hexagonal MnCo 0.78 Fe 0.22 Ge alloys, which undergoes a first-order phase transformation from paramagnetic hexagonal phase into ferromagnetic orthorhombic martensite on cooling. Owing to the magnetostructural coupling, large magnetocaloric effect (∆S M =−10.97 J•kg-1 •K-1) was obtained at 254 K. In-situ synchrotron high-energy X-ray diffraction experiments were conducted to reveal the detailed change in crystallographic structure of phases and the effect of applied magnetic field on phase transformation behaviors. An anomalously huge strain of 11.89% and volume expansion of 4.35% in unit-cell was obtained between martensite and parent phase across the transformation. Furthermore, the magnetic field-induced martensitic transformation was directly evidenced at 250 K, which eventually demonstrates the possibility to achieve magnetic-field-induced strain and large magnetocaloric effect simultaneously.
The Critical Behaviour and Magnetism of MnCoGe0.97Al0.03 Compounds
Crystals, 2022
The critical behaviour associated with the field-induced martensitic transformation heavily relies on the vacancy and transition of the magnetic phase in MnCoGe based-compounds. Due to this revelation, an intensive investigation was brought forth to study the substitution of Ge (atomic radius = 1.23 Å) by Al (atomic radius = 1.43 Å) in MnCoGe0.97Al0.03 alloy compound. The room-temperature X-ray diffraction indicated that the reflections were identified with the orthorhombic structure (TiNiSi-type, space group Pnma) and minor hexagonal structure (Ni2In-type, space group P63/mmc). The substitution of Al in the supersession of Ge transmuted the crystal structure from TiNiSi-type to Ni2In-type structure. The MnCoGe0.97Al0.03 compound’s magnetism was driven by interactions that are long in range, as indicated by the study of the critical behaviour in the proximity of TC. The magnetic measurement and neutron diffraction revealed that the structural transition took place with the decrease ...
The structural and magnetic properties of Ni2Mn1−xMxGa (M=Co, Cu)
Journal of Applied Physics, 2005
In Ni2MnGa (cubic structure of L21 type) a first order martensitic structural transition, from the parent cubic (austenitic) phase to a low temperature complex tetragonal structure, takes place at TM=202K, and ferromagnetic order in the austenitic phase sets at TC=376K. In this work, the Mn sites in Ni2MnGa have been partially substituted with magnetic Co and nonmagnetic Cu, and the influence of these substitutions on the structural and magnetic properties of Ni2Mn1−xMxGa (M=Co and Cu) have been studied by XRD and magnetization measurements. X-ray diffraction patterns indicate that the Co doped system possess a highly ordered Heusler alloy L21 type structure for 0.05<x<0.12, and the Cu doped compounds possess L21 structure for 0.05<x<0.10. The ferromagnetic ordering temperature increases with increasing Co concentration for this system, and rapidly decreases with increasing Cu concentration. Both systems show the increase in TM with increasing Co and Cu concentration. (T...
Martensitic transformation in a ferromagnetic Co–Ni–Ga single crystal
Materials Science and Engineering: A, 2004
The results of mechanical and magnetic characterization of martensitic transformation in a single crystalline ferromagnetic Co 49.0 Ni 22.0 Ga 29.0 alloy are presented. The transformation behavior is experimentally found to be characterized by an enlarged temperature hysteresis (30 K) on the calorimetric and magnetic susceptibility curves and stress hysteresis (over 200 MPa) on stress-strain dependencies. The linear dependence of the critical stress to induce martensite as a function of temperature is quantitatively described by a Clausius-Clapeyron equation. The different results are compared to the Ni-Mn-Ga system and discussed, resulting in scarce possibilities for this Co-Ni-Ga alloy to exhibit the large magnetostrain effect ("magnetic shape memory") observed in several Ni-Mn-Ga alloys.
Structural transformation and inverse magnetocaloric effect in Ni50Mn33In17
Journal of Magnetism and Magnetic Materials, 2019
The structural and magnetic properties of Ni 50 Mn 33 In 17 were investigated by means of synchrotron X-ray diffraction and magnetization measurements. In contrast to well established critical concentration of x ≤ 16.0 for Ni 50 Mn 50−x In x alloys to undergo structural transformation, we have found Ni 50 Mn 33 In 17 to undergo austenite to martensite structural transition around 170K. At room temperature, the Rietveld refinement of X-ray diffraction measurements revealed a L2 1 Heusler cubic structure belonging to F m3m space group while the low temperature martensite structure belongs to a monoclinic space group P 2/m. Temperature dependent magnetization measurements confirmed a near room temperature paramagnetic to ferromagnetic magnetic transition as well as a magnetostrucutral transition at ∼170K while magnetic field induced reverse martensite transformation was also confirmed. An inverse magnetocaloric effected associated with the magnetostructural transition is also observed with magnetic entropy change ∆ S M reaching ∼13.0 J/kg-K around 175K under field change of 0-6T. The inverse magnetocaloric effect occurs in a wide temperature range of 125-200 K with a relatively high refrigerant capacity of about 200 J/kg. This makes Ni 50 Mn 33 In 17 a promising magnetic refrigerant in the mentioned range of temperature as well as for further studies of effect of excess Mn on magnetic and structural properties of Ni 50 Mn 50−x In x alloys. 1. Introduction 1 In recent past, research into magnetic refrigeration 2 has seen a rapid growth mainly due to its potential for 3 more efficient and environmentally friendly refrigeration 4 as compared to the conventional gas compression technol-5 ogy [1, 2]. The process of magnetic refrigeration is based 6 on magnetocaloric effect which is associated to the change 7 in magnetic entropy of the system as a result of a magnetic 8 or magnetostructural transition. Typically, the materi-9 als undergoing second order magnetic transition (SOMT) 10 from ferromagnetic to paramagnetic phase bring about a 11 change in magnetic entropy of the system and give rise 12 to conventional MCE [3]. However after the discovery of 13 large MCE in Gd 5 (GeSi) 4 [4], the materials undergoing a 14 first order magnetostructural transition (FOMT) from an 15 austenite to martensite phase have attracted great inter-16 est. In this regard, the Ni 50 Mn 50−x In x off-stoichiometric 17 Heusler alloys have been drawing considerable interest due 18 to their temperature (or field) induced magnetostructural 19 transition resulting in significane change in magnetiza-20 tion. This change in magneization is responsible for re-21 lated physical properties like magnetoresistance, Hall ef-22 fect, shape memory effect and inverse magnetocaloric ef-23 fect in these materials [5, 6, 7, 8].
Large magnetostrain in polycrystalline Ni–Mn–In–Co
Applied Physics Letters, 2009
This letter reports the magnetic shape memory effect in a polycrystalline Ni 45.2 Mn 36.7 In 13 Co 5.1 alloy having the martensitic transformation around 310 K. An application of magnetic field shifts the transformation to lower temperatures by 6.7 K/T. Originating from the magnetically induced martensite-austenite transformation, a large magnetostrain of 0.25% at 310 K was observed in a textured polycrystalline Ni 45.2 Mn 36.7 In 13 Co 5.1 sample. Temperature, anisotropy, and cycling effects on the magnetostrain are discussed.
Materials, 2021
The aim of the present work is to study the influence of a partial substitution of Mn by Zr in MnCoGe alloys. The X-ray diffraction (XRD) studies revealed a coexistence of the orthorhombic TiNiSi-type and hexagonal Ni2In- type phases. The Rietveld analysis showed that the changes in lattice constants and content of recognized phases depended on the Zr addition. The occurrence of structural transformation was detected. This transformation was confirmed by analysis of the temperature dependence of exponent n given in the relation ΔSM = C·(BMAX)n. A decrease of the Curie temperature with an increase of the Zr content in the alloy composition was detected. The magnetic entropy changes were 6.93, 13.42, 3.96, and 2.94 J/(kg K) for Mn0.97Zr0.03CoGe, Mn0.95Zr0.05CoGe, Mn0.93Zr0.07CoGe, and Mn0.9Zr0.1CoGe, respectively. A significant rise in the magnetic entropy change for samples doped by Zr (x = 0.05) was caused by structural transformation.