Effect of selective substitution of Co for Ni or Mn on the superstructure and microstructural properties of Ni50Mn29Ga21

Kumar, Ajeet; Ramudu, M.; Seshubai, V.

doi:10.1016/j.jallcom.2011.05.064

Cited by 16 publications

(13 citation statements)

References 36 publications

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“…Ni 2+x−y Co y Mn 1−x Ga Ni 2 Mn 1+x−y Co y Ga 1−x Ni 2 Mn 1+x Ga 1−x−y Co y x = 0.16, 0 ≤ y ≤ 0.09 [34] x = 0.16, 0.0 ≤ y ≤ 0.26 [40] x = 0, 0 ≤ y ≤ 0.25 [38] Ni 2+x−y Co y MnGa 1−x Ni 2+x Mn 1−y Co y Ga 1−x x = 0, 0 ≤ y ≤ 0.2 [46] x = 0.12, 0 ≤ y ≤ 0.56 [35] x = 0.24, 0.16 ≤ y ≤ 0.32 [36] x = 0.16, y = 0.088 [37] x = 0.24, 0 ≤ y ≤ 0.32 [36] Ni 2+x Mn 1−x−y Co y Ga x = 0.16, 0 ≤ y ≤ 0.17 [47] Ni 2−y Co y Mn 1+x Ga 1−x x = 0, 0 ≤ y ≤ 0.25 [45] T m increases, x = 0, 0 ≤ y ≤ 0.2 [38] x = 0, 0.03 ≤ y ≤ 0.2 [38] T C weakly changes x = 0.16, 0 ≤ y ≤ 0.16 [40] x = 0.16, 0.04 ≤ y ≤ 0.14 [34] x = 0.16, 0 ≤ y ≤ 0.13 [42] T m increases, x = 0.16, 0 ≤ y ≤ 0.4 [44] T C weakly changes x = 0.24, 0.20 ≤ y ≤ 0.24 [39] 0 ≤ x ≤ 0.11, 0.068 ≤ x ≤ 0.232 [37] 0.2 ≤ x ≤ 0.28, 0 ≤ y ≤ 0.36 [19,41] 0.2 ≤ x ≤ 0.28, 012 ≤ y ≤ 0.32 [43] T m decreases, T C increases In general, it has been established that in Ni-Mn-Ga-Co compounds, the martensitic transformation temperature is found to increase with the substitution of Mn or Ga by Co and to decrease when replacing Ni by Co. Hence, the variation of the martensitic transition temperature follows the general trend that T m is proportional to the average valence electron number per atom (e/a) ratio.…”

Section: Substitution Of Co For Ni Substitution Of Co For Mn Substitumentioning

confidence: 99%

“…If using Co, it is expected that the Curie temperature will increase because of the strong ferromagnetic nature of Co. During the past decade, a series of investigations of the magnetic and structural properties of Co-doped Ni-rich and Mn-rich Ni-Mn-Ga Heusler alloys has been reported by different groups regarding the substitution of Co for Ni, Mn, as well as Ga. Since, in this paper, we present the results of ab initio calculations and Monte Carlo simulations of substitutional processes (mainly Co for Ni), we have gathered in Table 1 the investigations from the literature (without claiming to have a complete list of all investigations performed so far) [19,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Figure 1.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Substitution Of Co For Ni Substitution Of Co For Mn Substitumentioning

confidence: 99%

Section: Introductionmentioning

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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“…2 Heusler type Ni-Mn-X-Y (X = Ga, Sn, In and Sb, Y = Co and Fe) systems have attracted research interest owing to their multifunctional properties like magnetic shape memory, magnetocaloric effect, magnetoresistance, metamagnetic shape memory, and direct conversion of heat to electricity. [6][7][8][9][10][11][12][13][14][15][16] The above systems are also found to exhibit EB effect in the martensitic state. [16][17][18][19][20][21] Recently the Ni-Co-Mn-Sn system has attracted attention due to its magnetocaloric and EB effects.…”

Section: Introductionmentioning

confidence: 86%

Investigations on Ni-Co-Mn-Sn thin films: Effect of substrate temperature and Ar gas pressure on the martensitic transformations and exchange bias properties

Machavarapu

Jakob

2015

AIP Advances

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We report the effect of substrate temperature (TS) and Ar gas pressure (PD) on the martensitic transformations, magnetic and exchange bias (EB) properties in Heusler type Ni-Co-Mn-Sn epitaxial thin films. Martensitic transformation temperatures and EB fields at 5 K were found to increase with increasing TS. The observed maximum EB value of 320 Oe after field cooling in the film deposited at 650 ∘C is high among the values reported for Ni-Mn-Sn thin films which is attributed to the coexistence of ferromagnetic (FM) and antiferromagnetic (AF) phases in the martensitic state. In the case of PD variation, with increase in PD, martensitic transformation temperatures were increased and a sharp transformation was observed in the film deposited at 0.06 mbar. Magnetization values at 5 K were higher for increasing PD. These observations are attributed to the compositional shift. EB effect is also present in these films. Microstructural features observed using atomic force microscopy (AFM) shows a fine twinning and reduced precipitation with increase in PD, which is also confirmed from the scanning electron microscopy (SEM) images. EB effects in both series were confirmed from the training effect. Target ageing effect has been observed in the films deposited before and after ninety days of time interval. This has been confirmed both on substrate temperature and Ar gas pressure variations.

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“…Recently, cobaltdoped Ni-Mn-Ga alloys have generated great interest because of their ability to exhibit exciting phenomena such as metamagnetic transformations, [17] magnetic-fieldinduced martensitic transformations [18] and large magnetic entropy change across the transformations [19]. There have been many reports on the effect of Co-and Fe-doped either for Ni or for Mn on the variations in their martensitic transformation temperature (T M ), Curie temperature (T C ) and the magnetic properties [20][21][22]. Recently, we explored the role of cobalt site occupancy on the crystal structure, microstructure and melting point of Ni-Mn-Ga-Co alloys [22].…”

mentioning

confidence: 99%

“…There have been many reports on the effect of Co-and Fe-doped either for Ni or for Mn on the variations in their martensitic transformation temperature (T M ), Curie temperature (T C ) and the magnetic properties [20][21][22]. Recently, we explored the role of cobalt site occupancy on the crystal structure, microstructure and melting point of Ni-Mn-Ga-Co alloys [22]. Substitution of Co for Mn resulted in the stabilization of a nonmodulated tetragonal (NM) phase at higher Co content.…”

mentioning

confidence: 99%

Site preference of magnetic atoms in Ni–Mn–Ga–M (M = Co, Fe) ferromagnetic shape memory alloys

Ayila

Machavarapu

Vummethala

2011

Physica Status Solidi (b)

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Site preference of cobalt and iron atoms substituted in Ni-MnGa alloys is examined using the compositional dependence of saturation magnetization determined at 5 K. Variations in magnetization of Ni 50 Mn 25þx Ga 25ÀxÀy M y (M ¼ Co, Fe) alloys are systematically compared with the values computed for different possible configurations of site occupancies. The study reveals that the dopant atoms occupy the regular Mn site, rather than the vacant Ga site, with ferromagnetic exchange relative to the moments on Ni and Mn sublattices. The excess and displaced Mn atoms occupy the vacant Ga site with antiferromagnetic exchange. Site preference appears to have a correlation to the atomic volume of the elements. [4][5][6] has studied in detail the structural and magnetic properties of Ni-Mn-Ga alloys system with a focus on the composition dependence of transformation temperatures. The magnetic moment in Ni-Mn-Ga Heusler alloy is mainly localized on the Mn sites, as confirmed by both experiments [7,8] and theoretical calculations [9]. From magnetization measurements, Webster et al. [7] reported that the total saturation magnetic moment per formula unit (m B /f.u.) of Ni 2 MnGa is 4.17. The magnetic moment is localized primarily on the manganese atoms with m Mn $ 3.5 m B , while the moment on nickel atoms is quite small with m Ni $ 0.33 m B . From polarized neutron scattering and magnetization studies, Brown et al.

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Effect of selective substitution of Co for Ni or Mn on the superstructure and microstructural properties of Ni50Mn29Ga21

Cited by 16 publications

References 36 publications

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

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

Investigations on Ni-Co-Mn-Sn thin films: Effect of substrate temperature and Ar gas pressure on the martensitic transformations and exchange bias properties

Site preference of magnetic atoms in Ni–Mn–Ga–M (M = Co, Fe) ferromagnetic shape memory alloys

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