Magnetic Moment

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The magnetic property of a material is due to the existence of a magnetic moment (µ) in the material even in the absence of an applied magnetic field and from induction of magnetic moment in response to an applied magnetic field. Classically, a magnetic moment is equivalent to a current loop and it is a fundamental quantity defining the magnetic property. The magnetic moments of the nucleons are three orders of magnitude smaller than that of the electrons. The electronic magnetic moment has two sources. The magnetic moment is associated with spin and orbital angular momentum of electron. The spin and orbital components of magnetic moment of an electron is related to the respective angular momentum as µ = γ J. Where µ and J represent …show more content…

The modulation is a five layered (5M) martensite phase. Also, a stress-induced intermartensitic transformations to a body-centred monoclinic structure with seven (110) plane modulation (seven-layered martensite) and a body-centred tetragonal structure having c/a > 1 without modulation (non-modulated martensite) have been reported [1, 4, 5]. Non-modulated (NM) structure was observed in the alloys, which have high martensitic transformation temperature (Tm). These alloys are in Ms at room temperature. The X-ray and electron diffraction analysis signifies that, the structure is a face centered L10. The NM phase is the most stable among the martensitic structures. Webster et al., initially proposed the 5M martensite structure in Ni2MnGa alloy [28]. This martensite phase appeared below the room temperature and hence to study the structure, the transmission electron microscope (TEM) and electron diffraction was used. The modulation was observed as a four extra spot between the main reflections along the c* axis [110] in the reciprocal space. The 5M martensite of Ni2MnGa alloy was similar to the structure reported in Ni-Al-Mn alloy, in which the structure was reported as 10M martensite. Martynov and Kokorin observed the 7M martensite structure in Ni2MnGa alloy [29]. This kind of martensite has been observed through electron diffraction in the alloy. Thermodynamically, 7M martensite phase was considered as a metastable and intermediate phase. The 7M martensite has its own crystal structure, other than the nanotwin combination of the tetragonal NM martensite. The 7M martensite has orthorhombic lattice with c/a ~0.89. The researcher’s now call the 5M and 7M martensite structures as 10M and 14M martensite respectively by considering the number of atomic planes where 5M has 10 atomic planes and 7M has 14 atomic planes. Figure 1.3 shows the 10M and

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