Shape memory ferromagnets

Васильев, А. Н.; Buchelnikov, V. D.; Takagi, Toshiyuki; Ховайло, В. В.; Éstrin, É. I.

doi:10.3367/ufnr.0173.200306a.0577

Cited by 54 publications

(25 citation statements)

References 184 publications

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“…1. The experimental results obtained evidence that the ∆T dependence has a peak at T ≈ 340 K. This temperature corresponds to the temperature of MSPT [1]. A statistical model is suggested for the theoretical description of the alloy properties near MSPT.…”

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confidence: 70%

“…In Ni-Mn-Ga alloys, the martensitic transition temperature is very sensitive to composition, which is very important for practical applications of these alloys. For instance, upon a partial substitution of Mn for Ni the martensitic transition temperature T m increases and Curie temperature T C decreases until they merge in one first-order magnetostructural phase transition (MSPT) [1]. The values of MCE in the vicinity of such a transition are likely to be maximal.…”

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confidence: 99%

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Magnetocaloric effect and magnetization in a Ni–Mn–Ga Heusler alloy in the vicinity of magnetostructural transition

Aliev

Batdalov

Bosko

et al. 2004

Journal of Magnetism and Magnetic Materials

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The magnetic and thermodynamic properties of a Ni2.19Mn0.81Ga alloy with coupled magnetic and structural (martensitic) phase transitions were studied experimentally and theoretically. The magnetocaloric effect was measured by a direct method in magnetic fields 0−26 kOe at temperatures close to the magnetostructural transition temperature. For theoretical description of the alloy properties near the magnetostructural transition a statistical model is suggested, that takes into account the coexistence of martensite and austenite domains in the vicinity of martensite transformation point.Keywords: Ferromagnetism; Magnetostructural phase transition; Magnetization; Magnetocaloric effectIn recent year Ni 2 MnGa-based ferromagnetic shape memory alloys have attracted considerable attention as a new class of actuator materials (see, for a recent review, Ref.[1]). Giant magnetocaloric effect (MCE) has also been observed in these alloys. Solid state materials with a large MCE are considered to be very perspective in creation of solid state refrigerators with high efficiency, manufacturability and ecological compatibility (Ref. [2] and references therein). In Ni-Mn-Ga alloys, the martensitic transition temperature is very sensitive to composition, which is very important for practical applications of these alloys. For instance, upon a partial substitution of Mn for Ni the martensitic transition temperature T m increases and Curie temperature T C decreases until they merge in one first-order magnetostructural phase transition (MSPT) [1]. The values of MCE in the vicinity of such a transition are likely to be maximal. The aim of our work has been to study, experimentally and theoretically, magnetic and thermodynamic properties of Ni 2.19 Mn 0.81 Ga alloy with MSPT and to determine directly the magnitude of MCE.Polycrystalline Ni 2.19 Mn 0.81 Ga alloy was prepared by a conventional arc-melting method in argon atmosphere. MCE was measured by a direct method in a calorimetric system at constant temperatures in the vicinity of MSPT. The sample for the measurement of MCE was fixed by glass wires of 10 mm in diameter glued to the sample. The change in the temperature of the sample, ∆T , with the change in magnetic field, ∆H, was measured by a differential thermocouple. A cooper screen was placed near the sample in order to decrease radiational losses. The magnetic field up to 26 kOe was created by an electromagnet.The temperature dependence of ∆T at turning the magnetic field off is presented in Fig. 1. The experimental results obtained evidence that the ∆T dependence has a peak at T ≈ 340 K. This temperature corresponds A statistical model is suggested for the theoretical description of the alloy properties near MSPT. The model takes into account coexistence of three types of martensitic and one type of austenitic structural domains in the vicinity of MSPT point [3,4]. Each structural domain is divided by 180• magnetic domains. It is postulated that the rate of transformation between structural domains is proportional to the net p...

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confidence: 70%

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confidence: 99%

Magnetocaloric effect and magnetization in a Ni–Mn–Ga Heusler alloy in the vicinity of magnetostructural transition

Aliev

Batdalov

Bosko

et al. 2004

Journal of Magnetism and Magnetic Materials

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“…The best achievements in this field are related to the Heusler alloys Ni 2+x+y Mn 1-x Ga 1-y [1]. An effort is made to expand the range of MCSME alloys.…”

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Study of Co-Ni-Al Alloys with Magnetically Controlled Shape Memory Effect

Kositsyna

Завалишин

2009

MSF

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Abstract. The methods of electron microscopy, resistometry and magnetometry are used to study ten (36-38)Co − (32-36)Ni − (27-30)Al (at. %) alloys. Cast coarse-crystalline and microcrystalline alloys made by melt spinning in a helium atmosphere are considered. It is shown that the martensite start temperature M s becomes 30-50°C lower as grains are refined to 1 µ m. Replacement of 1 at. % cobalt by nickel and 1 at. % aluminum by nickel makes the temperature interval of the В2 ↔ L1 0 martensite transformation (30-60)°C and (100-110)°C higher respectively. The martensite transformation hysteresis is about 100 degrees. The melt-spun Co 38 Ni 34 Al 28 alloy with the transformation temperatures М s = 31°С, М f = -34°С, А s = -6°С, А f = 70°С and Т с = 98°С is a material possessing the magnetically controlled shape memory effect.

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“…Among ferromagnetic (FM) materials having acceptable magnetocaloric properties, Ni-Mn-Ga Heusler alloys have been widely investigated by experimental and theoretical methods in view of their potential applications as intelligent functional materials [1][2][3][4][5]. The multifunctional properties usually appear across a martensitic transformation due to the strong coupling of crystal structure and magnetic order.…”

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confidence: 99%

Ab Initio and Monte Carlo Approaches For the Magnetocaloric Effect in Co- and In-Doped Ni-Mn-Ga Heusler Alloys

Sokolovskiy

Grünebohm

Buchelnikov

et al. 2014

Entropy

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Abstract:The complex magnetic and structural properties of Co-doped Ni-Mn-Ga Heusler alloys have been investigated by using a combination of first-principles calculations and classical Monte Carlo simulations. We have restricted the investigations to systems with 0, 5 and 9 at% Co. Ab initio calculations show the presence of the ferrimagnetic order of austenite and martensite depending on the composition, where the excess Mn atoms on Ga sites show reversed spin configurations. Stable ferrimagnetic martensite is found for systems with 0 (5) at% Co and a c/a ratio of 1.31 (1.28), respectively, leading to a strong competition of ferro-and antiferro-magnetic exchange interactions between nearest neighbor Mn atoms. The Monte Carlo simulations with ab initio exchange coupling constants as input parameters allow one to discuss the behavior at finite temperatures and to determine magnetic transition temperatures. The Curie temperature of austenite is found to increase with Co, while the Curie temperature of martensite decreases with increasing Co content. This behavior can be attributed to the stronger Co-Mn, Mn-Mn and Mn-Ni exchange coupling constants in austenite compared to the corresponding ones in martensite. The crossover from a direct to inverse magnetocaloric effect in Ni-Mn-Ga due to the substitution of Ni by Co leads to the appearance of a "paramagnetic gap" in the martensitic phase. Doping with In increases the magnetic jump at the martensitic transition temperature. The simulated magnetic and magnetocaloric properties of Co-and In-doped Ni-Mn-Ga alloys are in good qualitative agreement with the available experimental data.

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Shape memory ferromagnets

Cited by 54 publications

References 184 publications

Magnetocaloric effect and magnetization in a Ni–Mn–Ga Heusler alloy in the vicinity of magnetostructural transition

Magnetocaloric effect and magnetization in a Ni–Mn–Ga Heusler alloy in the vicinity of magnetostructural transition

Study of Co-Ni-Al Alloys with Magnetically Controlled Shape Memory Effect

Ab Initio and Monte Carlo Approaches For the Magnetocaloric Effect in Co- and In-Doped Ni-Mn-Ga Heusler Alloys

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