Magnetic, microstructural and magnetoresistive properties of Heusler melt spun ribbons (original) (raw)
Related papers
Journal of Magnetism and Magnetic Materials, 2009
We outline the microstructural, martensitic transformation and magnetic properties of Heusler alloys with starting compositions Ni 50 Mn 37 Sn 13 , Ni 50 Mn 36 In 14 , and Mn 50 Ni 40 In 10 , produced by melt spinning. The ribbons were obtained in argon environment at a high wheel linear speed of 48 m s À1 (typical dimensions: 1.2-2.0 mm in width, 4-12 mm in length, and 7-12 mm in thickness). EDS microanalysis showed that the resulting average elemental chemical composition is slightly shifted with respect to the starting one. Ribbons are fully crystalline and tend to show a highly ordered columnar-like microstructure with grains running through the entire ribbon thickness; the larger dimension of the grains is perpendicular to the ribbon plane. As-spun alloys were single-phase with ferromagnetic bcc L2 1 austenite as high-temperature parent phase. At low temperatures austenite transforms into a structurally modulated martensite with a lattice symmetry that depends on the system (7 M orthorhombic for Ni 50 Mn 37 Sn 13 , 10 M monoclinic for Ni 50 Mn 36 In 14 , and 14 M monoclinic for Mn 50 Ni 40 In 10 ). Magnetization isotherms measured in the temperature interval where martensite thermally transforms into austenite confirmed the occurrence of field-induced reverse martensitic transition in the alloys studied.
Microstructure and magnetic properties of Ni[sub 50]Mn[sub 37]Sn[sub 13] Heusler alloy ribbons
Journal of Applied Physics, 2008
The Heusler alloy Ni 50 Mn 37 Sn 13 was successfully produced as ribbon flakes of thickness around 7-10 m melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be M S = 218 K, M f = 207 K, A S = 224 K, and A f = 232 K; the thermal hysteresis of the transformation is 15 K. Ferromagnetic L2 1 bcc austenite phase shows a Curie point of 313 K, with cell parameter a = 0.5971͑5͒ nm at 298 K, transforming into a modulated 7M orthorhombic martensite with a = 0.6121͑7͒ nm, b = 0.6058͑8͒ nm, and c = 0.5660͑2͒ nm, at 150 K.
Microstructure and magnetic properties of NiMnSn Heusler alloy ribbons
Journal of Applied …, 2008
The Heusler alloy Ni(50)Mn(37)Sn(13) was successfully produced as ribbon flakes of thickness around 7-10 mu m melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be M(S)=218 K, M(f)=207 K, A(S)=224 K, and A(f)=232 K; the thermal hysteresis of the transformation is 15 K. Ferromagnetic L2(1) bcc austenite phase shows a Curie point of 313 K, with cell parameter a=0.5971(5) nm at 298 K, transforming into a modulated 7M orthorhombic martensite with a=0.6121(7) nm, b=0.6058(8) nm, and c=0.5660(2) nm, at 150 K.
Microstructure and magnetic properties of Ni50Mn37Sn13 Heusler alloy ribbons
Journal of Applied Physics, 2008
The Heusler alloy Ni 50 Mn 37 Sn 13 was successfully produced as ribbon flakes of thickness around 7-10 m melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be M S = 218 K, M f = 207 K, A S = 224 K, and A f = 232 K; the thermal hysteresis of the transformation is 15 K. Ferromagnetic L2 1 bcc austenite phase shows a Curie point of 313 K, with cell parameter a = 0.5971͑5͒ nm at 298 K, transforming into a modulated 7M orthorhombic martensite with a = 0.6121͑7͒ nm, b = 0.6058͑8͒ nm, and c = 0.5660͑2͒ nm, at 150 K.
Materials Science …, 2010
We report the effect of a short-time vacuum annealing (1073 K during 10 minutes) on structural phase transition temperatures and magneto-structural properties of as-quenched ribbons of the Heusler alloy Ni 50.6 Mn 34.5 In 14.9. This alloy crystallizes in a single phase cubic B2-type austenite with a Curie point of T C A =284 K that with the lowering in temperature transforms into a martensite with T C M ≈185 K. The direct and reverse martensitic phase transition temperatures were M S =257 K, M f = 221 K, A S = 239 K, and A f = 266 K. After annealing austenite shows the highly ordered L2 1type structure while the average chemical composition as well as the structural and magnetic transition temperatures were shifted to Ni 50.2 Mn 34.3 In 15.
Structural behavior of Ni-Mn-(In, Sn) Heusler melt spun ribbons
ESOMAT 2009 - 8th European Symposium on Martensitic Transformations, 2009
In present contribution we discuss the structural properties of the austenite and martensite phases that form in as-spun ribbons of some selected compositions of the ternary system Ni 50 Mn 50-x (In,Sn) x , their characteristic crystallographic texture and the effect of vacuum annealing. X-Ray diffraction analysis showed that in all the cases austenite crystallized in an ordered cubic L2 1 -type structure. For thermally annealed samples diffraction lines becomes narrower in comparison with those of as-quenched samples, cell parameters tend reduce and crystallographic texture is preserved and improved. Furthermore, the structure and the martensitic temperature transformation can significantly differ from that of bulk alloys. Thus, materials with different structure, magnetoelastic behavior and transformation temperatures can be produced by melt spinning controlling starting composition and quenching conditions. In textured ribbons, the columnar, almost 1-dimensional, shape of the grains makes structural changes more difficult than in bulk materials (3-dimensional shape), thus explaining the differences observed in their structure and temperature magnitudes involved.
Magnetic and Martensitic Transformations in Ni46Mn41.5-xFexSn12.5 Melt Spun Ribbons
Materials Science Forum, 2014
Four alloys with nominal compositions Ni 46 Mn 41.5-x Fe x Sn 12.5 (x=0, 2, 4, 6 at.%) were cast in an induction vacuum furnace and homogenized. Then they were melted in quartz tubes and ejected onto a rotating copper wheel to produce ribbons. The X-Ray phase analyses of as melt spun ribbons have shown that in both, the ternary as well as in the quaternary alloys a single phase of the Heusler L2 1 type ordered structure was found. The characteristic temperatures of magnetic (T C ) and martensitic (M s ) transformations were determined by a vibrating sample magnetometer (VSM). Both the M s and T C increase with the increase of Fe content in all alloys, which is in accordance with the theory of valence electron concentration (e/a) influence on M s . The phase structures, chemical compositions, grains sizes and type of microsegregation were characterized by use of transmission electron microscope (TEM). The equi-axed grains of size from 0.95 to 1.7 µm were observed in all ribbons. The grains posses the L2 1 structure at room temperature, however in the alloys with higher Fe content the different type of martensite was observed at the grain boundaries of L2 1 phase. Appearance of this martensite was explained in relation to microsegregation of particular elements during melt spinning process and simultaneous change in the e/a ratio.
Materials
Ni–Mn-based Heusler alloys are known to demonstrate magnetic shape memory and giant magnetocaloric effect (MCE). These effects depend on the phases, crystallographic and magnetic phase transitions, and the crystallographic texture characteristics. These structural characteristics, in turn, are a function of the processing parameters. In the current work, Ni55.5Mn18.8Ga24Si1.7 Heusler alloy was processed by melt-spinning under a helium atmosphere. This process results in a fine microstructure. The ribbon that was produced with a narrower nozzle width, faster wheel speed, and higher cast temperature, indicating a faster cooling rate, had double the magnetic entropy change close to room temperature. However, the other ribbon demonstrated a large entropy change over a broader temperature range, extending its usability. The effect of the melt-spinning process parameters on the developing microstructure, crystallographic structure and texture, transformation temperatures, and the magnetic...
Influence of Fe doping and magnetic field on martensitic transition in Ni-Mn-Sn melt-spun ribbons
Mn-rich Ni-Mn-Sn metamagnetic shape memory alloys exhibiting magnetostructural transformation are of a great potential as the base materials for solid-state refrigeration. With the aim of fine tuning of the transformation characteristics and improving functional properties, in the present work we have fabricated polycrystalline Ni 50-x Fe x Mn 40 Sn 10 (x = 0, 2, 4, 6, 8 at.%) melt-spun ribbons, starting from the base alloy with x = 0, which is weakly magnetic in both austenitic and martensitic phases. By exploring martensitic transformation (MT) and magnetic behaviors as a function of Fe doping and magnetic field, we have found that Fe and/or magnetic field reduce the MT temperature and Curie temperature of austenite phase, becoming closer to each other as the Fe-content increases, accompanied by an increase of the magnetic moment of austenite, magnetization jump at MT, transformation volume, and magnetic contribution, ∆S M , to the total entropy change at MT. The ribbons present moderate values of ∆S M equal to 11 J kg-1 K-1 at 5 T for x = 8, moderate thermal hysteresis (10-14 K) nearly independent of Fe doping or magnetic field, and adjustable structural and magnetic transition temperatures close to room temperature.
We report features of microstructure, martensitic transformation, magnetic properties and magnetoca-loric effect in three off-stoichiometric Ni 45 Mn 44 In 11 , Ni 47 Mn 41 In 12 and Ni 48 Mn 39 In 13 (nominal-compositions) alloys ribbons. They were selected in the 7.8o e/ao 8.0 range, being e/a the valence electron concentration per atom, one of the parameters that determines functional properties displayed by these alloys near room-temperature. Although the real composition is shifted from nominal one in each sample, its influence on all here studied properties at the temperature range of 50–400 K is analyzed. Especially, the role played by Ni content in the decrease of magnetization observed in two alloys with respect to the third one with the lowest e/a. Ni content effect on the antiferromagnetic interaction present in the martensitic phase of the alloys ribbons is also evidenced.