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The phase stability, martensitic transformation, and magnetic and mechanical properties of (Ni2- xCo xMn1.5Ti0.5)1- yB y (0 ≤ x ≤ 0.625; y = 0.03 and 0.06) alloys are systematically studied through the first-principles calculations method. The Co and B atoms are inclined to be aggregated distribution in the Ni2Mn1.5Ti0.5 alloy, and the phase stability of the austenite and non-modulated (NM) martensite decreases by co-doping. The ferromagnetic activation effect in the austenite occurs when x = 0.03 and y = 0.625. The magnetism of the austenite changes from an antiferromagnetic to a ferromagnetic state, which is ascribed to the elongation of the nearest neighboring distance of Mn–Mn, the nearest Mn–Mn distance increases from 2.50–2.79 to 2.90–2.94 Å, while the NM martensite always shows antiferromagnetism. Additionally, the doped B accelerates the change from antiferromagnetic to ferromagnetic for the austenite, but B-doping decreases the stability of the whole alloy system. The Co and B co-doping increases the stiffness of the NiMnTi alloy but decreases toughness and plasticity. However, the toughness and plasticity of the NiCoMnTiB alloy are better than those of the NiMnTiB alloy, indicating that the Co doping increases the d-orbital hybridization in the NiMnTiB alloy. The above results are expected to support the performance design of the NiMnTi-based alloy.

In this work, we present the observation of large low-temperature magnetocaloric effect and good mechanical properties in the Ni36Co13Mn35Ti16 alloy. The phase transition behaviors, magnetocaloric effect, and mechanical properties for the Ni36Co13Mn35Ti16 non-textured polycrystalline alloy were systematically investigated. Under the magnetic field changes of 5 T, a typical meta-magnetic behavior with a large magnetization change of about 110 A m2 kg−1 between the austenite and martensite can be observed, the maximum magnetic entropy changes (ΔS m) of the Ni36Co13Mn35Ti16 alloy is ∼16.1 J kg−1 K−1 at 148 K. Furthermore, the maximum compressive stress and strain are 894 MPa and 8.0%, respectively. The scanning electron microscope and first-principles calculations were used to analyze the fracture mechanism and the bonding interaction. In the combination of the large low-temperature magnetocaloric effect and good mechanical properties, the Ni36Co13Mn35Ti16 alloy has a good prospect for low-temperature magnetic refrigeration applications.

A calculation model for magnetic domain configuration and magnetostriction in grain-oriented silicon steel under tension stress is proposed. The surface lancet and transverse domains in demagnetization and magnetization states are calculated as a function of grain orientation and tension stress. Magnetostriction is calculated by incorporating the critical conditions for disappearance and reappearance of the transverse domain during the magnetization process. The magnetic domain and magnetostriction vary obviously with tension stress and misorientation angle, especially in the ranges of 5–20 MPa and 1°–5°. Negative magnetostriction is quantitatively evaluated in terms of the contribution of the reappeared transverse domain. The calculation model can accurately characterize the magnetostriction of grain-oriented silicon steel under tension stress based on the normal distribution of misorientation angle.

International audience; In the present work, Co-23.0 at. % Pt and Co-23.0 at. % Pt-3.67 at. % P thin films with their c-axis perpendicular to the substrate surface were fabricated on a glass substrate by DC magnetron sputtering. X-ray diffraction and transmission electron microscopic analyses demonstrate that the doping of P improves the c-axis alignment and forms P-rich non-magnetic phase at grain boundary areas, the latter resulting in inter-granular exchange decoupling between Co-Pt grains. The improved c-axis alignment and the inter-granular exchange decoupling give rise to the increase of the out of plane coercivity and the squareness of the Co-Pt-P films.

Strong Goss texture ({110}〈001〉) was successfully developed by secondary recrystallization in Fe81Ga19 sheets without conventional application of inhibitor or surface energy effect as grain-oriented silicon steel. Goss grains cover 90% surface area of annealed sheet, and the magnetostriction coefficient reaches up to 262 ppm. The primary recrystallization microstructure and texture provide the prerequisites for nucleation and abnormal grain growth of secondary Goss grains. The dispersedly distributed Goss grains do not exhibit an evident advantage in grain size and number, and the normal grain growth of matrix grains can be inhibited by low-angle grain boundaries before onset of secondary recrystallization. The existence of low-angle grain boundaries is proposed to be an important factor for the occurrence of secondary recrystallization in binary Fe-Ga sheets based on grain boundary character distribution analysis.

The textured Pr2Fe14B nanoflakes were produced by surfactant-assisted ball milling (SABM). Single phase tetragonal structure was characterized for the samples before and after SABM by X-ray diffraction (XRD). The thickness and length of the as-milled flakes are mainly in the range of 50–150 nm and 0.5–2 μm, respectively. For the field-aligned Pr2Fe14B nanoflakes, the out-of-plane texture (the easy magnetization direction (EMD) along the c-axis) is indicated from the increasing (00l) peaks in the XRD patterns. SEM image demonstrates that the EMD is parallel to flaky surface, which is different from the RCo5 (R = rare earth) system with EMD perpendicular to the surface. We propose a hypothesis that the easy glide planes are related with the area of crystal planes. In addition, a large coercivity Hc = 3.9 kOe is observed in the Pr2Fe14B flakes with strong texture.

The microstructure, crystal structure, and magnetic properties of low-temperature phase (LTP) Mn-Bi nanosheets, prepared by surfactant assistant high-energy ball milling (SA-HEBM) with oleylamine and oleic acid as the surfactant, were examined with scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. Effect of ball-milling time on the coercivity of LTP Mn-Bi nanosheets was systematically investigated. Results show that the high energy ball milling time from tens of minutes to several hours results in the coercivity increase of Mn-Bi powders and peak values of 14.3 kOe around 10 h. LTP Mn-Bi nanosheets are characterized by an average thickness of tens of nanometers, an average diameter of ∼1.5 μm, and possess a relatively large aspect ratio, an ultra-high room temperature coercivity of 22.3 kOe, a significant geometrical and magnetic anisotropy, and a strong (00l) crystal texture. Magnetization and demagnetization behaviors reveal that wall pinning is the dominant coercivity mechanism in these LTP Mn-Bi nanosheets. The ultrafine grain refinement introduced by the SA-HEBM process contribute to the ultra-high coercivity of LTP Mn-Bi nanosheets and a large number of defects put a powerful pinning effect on the magnetic domain movement, simultaneously. Further magnetic measurement at 437 K shows that a high coercivity of 17.8 kOe and a strong positive temperature coefficient of coercivity existed in the bonded permanent magnet made by LTP Mn-Bi nanosheets.

The effect of the milling time on the structure, morphology, coercivity, and remanence ratio of textured PrCo5 nanoflakes produced by low power surfactant-assisted ball milling (SABM) was investigated. The X-ray powder diffraction (XRD) patterns indicate that the SABM PrCo5 samples are all CaCu5-type hexagonal structure. The average grain size is smaller than 10 nm when the SABM time is equal to or longer than 5.5 h. The thickness of nanoflakes is mainly in the range of 50−100 nm while the length is 0.5−5 μm when the SABM time reaches 8 h. For the field-aligned PrCo5 nanoflakes, the out-of-plane texture is indicated from the increasing (0 0 l) peaks in the XRD patterns, and the easy magnetization direction is perpendicular to the flake surface. The strong texture of PrCo5 nanoflakes leads to a large coercivity Hc (7.8 kOe) and obvious anisotropic magnetic behaviors for the aligned samples.

Ni-Mn-In is a novel type of magnetic shape memory alloy. It shows that the martensitic transition from the ferromagnetic austenite to the antiferro- or paramagnetic martensite, which is different from the well-known Ni-Mn-Ga alloy, can be reversed by a magnetic field. We present the results of the crystallographic, magnetic, and electronic structures of Ni2MnIn alloy by means of the ab initio calculations within the framework of density functional theory using Vienna ab initio software package. Furthermore, the effects of substitution of Mn by Fe or Co have been systematically investigated in this paper.

Fe–6.5wt.%Si thin sheets were successfully produced by conventional rolling and annealing methods. The deformation and recrystallization textures were investigated by means of x-ray diffraction and electron backscattered diffraction analysis. It was found that a strong {001}〈210〉 recrystallization texture was obtained and the magnetic property was significantly improved under the appropriate rolling temperature. The formation of the {001}〈210〉 texture was explained in terms of preferred nucleation by the strain-induced boundary migration mechanism and selective growth by grain size advantage established during primary recrystallization.

The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni2XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first–principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni2MnGa have been calculated. The formation energies of the cubic phase of Ni2XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni2MnGa to Ni2CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below EF. There are two bond types existing in Ni2XGa: one is between neighboring Ni atoms in Ni2MnGa; the other is between Ni and X atoms in Ni2FeGa and ...

The crystallographic and magnetic structures of the Ni2XGa (X=Mn, Fe, Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The formation energies of several kinds of defects (atomic exchange, antisite, vacancy) are estimated. The Ga atoms stabilize the cubic structure, and the effect of X atoms on the structural stability is opposite. For most cases of the site occupation, the excess atoms of the rich component directly occupy the site(s) of the deficient one(s), except for Ga-rich Ni-deficient type. The magnitude of the variation in Ni moments is much larger than that of Mn in defective Ni2XGa. The value of Ni magnetic moment sensitively depends on the distance between Ni and X. Excess Mn could be ferromagnetic or antiferromagnetic, depending on the distance between the neighboring Mn atoms.

We report here that the ball-milling process induces the phase transformation from the tetragonal structure to the disordered face-centered-cubic structure in Ni2MnGa ferromagnetic shape-memory alloys. The in situ high-energy x-ray diffraction analyses reveal that an intermediate phase, which is characterized by amorphous structure, controls the transformation kinetics during the postannealing process. Completely different from their coarse-grained counterparts, the ferromagnetic Ni2MnGa nanoparticles undergo various sequences of structural transitions that are tailored by the crystallite size, atomic order, and intrinsic magnetic structure.

The fourth‐rank tensor averaging method due to Morris [J. Appl. Phys. 40, 447 (1969)] is further extended to textured cubic materials with no physical symmetry. The coefficients of the nine linearly independent elements of the transformation matrix [Tijkl], as well as the relevant fifty‐four relations for the calculation of the remaining Tijkl, are derived and presented in tabular form. It is also noted that for orthotropic physical symmetry and cubic crystal symmetry, the number of the linearly independent elements Tijkl is three instead of 15. The applicability of the present analysis is demonstrated by a comparative study.