Incommensurate modulated structure of the ferromagnetic shape-memory Ni2MnGa martensite

Righi, Lara; Albertini, F.; Calestani, G.; Pareti, L.; Paoluzi, A.; Ritter, C.; Algarabel, P. A.; Morellón, L.; Ibarra, M. R.

doi:10.1016/j.jssc.2006.07.005

Cited by 93 publications

(119 citation statements)

References 26 publications

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“…Therefore, we have investigated modulated martensitic phases by powder X-ray/neutron diffraction. Our results indicate the presence of incommensurate and commensurate modulation properly described within superspace approach [13][14][15]. The obtained crystal structures clarify a series of critical points concerning the structural study of Ni-Mn-Ga martensitic phases.…”

Section: Introductionsupporting

confidence: 65%

“…The two descriptions seem to be in contrast and this discrepancy was never clarified. This structural problem has been therefore re-investigated taking into account all the suitable information present in literature [13]. It has been demonstrated that, in agreement with what observed by A. Zheludev et al [18], this phase presents an incommensurate modulation whose structure has been solved within superspace approach [16].…”

Section: The "5m" Familymentioning

confidence: 56%

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Incommensurate and Commensurate Structural Modulation in Martensitic Phases of FSMA

Righi

Albertini

Paoluzi

et al. 2009

MSF

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Abstract. Magnetic and structural properties in multifunctional FSMA (Ferromagnetic Shape Memory Alloys) belonging to Heusler family are frequently related to the occurrence of structural modulation in martensitic phases. The highest MFIS (Magnetic Field Induced Strain) effect has been observed in Ni-Mn-Ga alloys showing martensitic modulated structures. Depending on the composition, pressure and temperature conditions, this periodic structural distortion, consisting of shuffling of atomic layers along specific crystallographic directions, accompanies the martensitic transformation. Over the years, different modulated martensitic structures have been observed and classified depending upon the periodicity of corresponding superstructure (nM with n=3, 5, 6, 7, 12 etc). On the other hand, it has been demonstrated that in most cases such structural modulation is incommensurate and the crystal structure can be solved by applying superspace approach. The crystallographic representation of different modulated structures, obtained by structure refinement on powder diffraction data, suggests a unified description where every different "nM" periodicity can be straightforwardly represented. It will be presented an overview illustrating structural features of several displacive modulated martensitic lattices. For a specific Ni-Mn-Ga composition, the evolution of structural modulation upon temperature change will be illustrated.

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Section: Introductionsupporting

confidence: 65%

Section: The "5m" Familymentioning

confidence: 56%

Incommensurate and Commensurate Structural Modulation in Martensitic Phases of FSMA

Righi

Albertini

Paoluzi

et al. 2009

MSF

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“…The higher resolution and high intensity SXRPD data used in the present study shows not only well defined main reflections but also satellites reflection up to the third order, which enabled us to quantify the modulation wave vector precisely, as compared to the earlier low resolution XRD study using rotating anode data [23].…”

Section: Introductionmentioning

confidence: 56%

“…[24] However, several workers have reported that the modulated phase of Ni 2 MnGa possesses an incommensurate structure. On the basis of Rietveld refinement in the (3+1) dimensional superspace using medium resolution laboratory source x-ray powder diffraction data, Righi et al [23] like modulations with four and six superlattice spots between the main austenite peaks have been reported [17,20]. Apparently the composition of the sample has a very crucial role in deciding the nature of the modulation.…”

Section: Introductionmentioning

confidence: 99%

High-resolution synchrotron x-ray powder diffraction study of the incommensurate modulation in the martensite phase ofNi2MnGa: Evidence for nearly 7M modulation and phason broadening

et al. 2014

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The modulated structure of the martensite phase of Ni 2 MnGa is revisited using high resolution synchrotron x-ray powder diffraction (SXRPD) measurements, which reveals higher order satellite reflections up to the 3 rd order and phason broadening of the satellite peaks. The structure refinement, using the (3+1) dimensional superspace group approach, shows that the modulated structure of Ni 2 MnGa can be described by orthorhombic superspace group 2

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“…Remarkably, the crystallographic structure of the martensitic phase can be tuned by changing composition from modulated (commensurate and incommensurate) monoclinic 10M and 14M structures to non-modulated tetragonal [25][26][27]. Structural relationships between lattice parameters in the martensitic phase and austenitic and martensitic lattice parameters determine respectively the maximum possible strain achievable by magnetic field induced variant reorientation and by magnetic field induced transformation (MFIS) in single crystals.…”

Section: Introductionmentioning

confidence: 99%

Co and In Doped Ni-Mn-Ga Magnetic Shape Memory Alloys: A Thorough Structural, Magnetic and Magnetocaloric Study

Fabbrici

Porcari

Cugini

et al. 2014

Entropy

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Abstract:In Ni-Mn-Ga ferromagnetic shape memory alloys, Co-doping plays a major role in determining a peculiar phase diagram where, besides a change in the critical temperatures, a change of number, order and nature of phase transitions (e.g., from ferromagnetic to paramagnetic or from paramagnetic to ferromagnetic, on heating) can be obtained, together with a change in the giant magnetocaloric effect from direct to inverse. Here we present a thorough study of the intrinsic magnetic and structural properties, including their dependence on hydrostatic pressure, that are at the basis of the multifunctional behavior of Co and In-doped alloys. We study in depth their magnetocaloric properties, taking advantage of complementary calorimetric and magnetic techniques, and show that if a proper measurement protocol is adopted they all merge to the same values, even in case of first order transitions. A simplified model for the estimation of the adiabatic temperature change that relies only on indirect measurements is OPEN ACCESSEntropy 2014, 16 2205 proposed, allowing for the quick and reliable evaluation of the magnetocaloric potentiality of new materials starting from readily available magnetic measurements.

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Incommensurate modulated structure of the ferromagnetic shape-memory Ni2MnGa martensite

Cited by 93 publications

References 26 publications

Incommensurate and Commensurate Structural Modulation in Martensitic Phases of FSMA

Incommensurate and Commensurate Structural Modulation in Martensitic Phases of FSMA

High-resolution synchrotron x-ray powder diffraction study of the incommensurate modulation in the martensite phase ofNi2MnGa: Evidence for nearly 7M modulation and phason broadening

Co and In Doped Ni-Mn-Ga Magnetic Shape Memory Alloys: A Thorough Structural, Magnetic and Magnetocaloric Study

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