Himalay Basumatary

Microstructure and magnetostriction of melt-spun Fe73Ga27 ribbon

Melt spun ribbon of Fe73Ga27 was prepared and characterized for microstructural features and magnetostriction. The phase equilibria observed from structural investigations have been correlated with Mossbauer studies. The magnetostriction of the melt spun ribbon has been found to be significantly large compared to the bulk sample. The large magnetostriction is attributed to the absence of ordered fcc (L12) phase in the melt spun ribbon, which is otherwise seen in slow cooled bulk Fe73Ga27 alloy.

Magnetostrictive Fe73Ga27 nanocontacts for low-field conductance switching

The electrical conductance G of magnetostrictive nanocontacts made from Galfenol (Fe73Ga27) can be reproducibly switched between “on” and “off” states in a low magnetic field of ∼20–30 mT at 10 K. The switching behavior is in agreement with the magnetic field dependence of the magnetostriction inferred from the magnetization behavior, causing a positive magnetostrictive strain along the magnetic field. The repeated magnetic-field cycling leads to a stable contact geometry and to a robust contact configuration with a very low hysteresis of ∼1 mT between opening and closing the contact due to a training effect. Non-integral multiples of the conductance quantum G0 observed for G > G0 are attributed to electron backscattering at defect sites in the electrodes near the contact interface. When the contact is closed either mechanically or by magnetic field, the conductance shows an exponential behavior below G0 due to electron tunneling. This allows to estimate the magnetostriction λ = 4 × 10−5 at 10 K. The resu...

Design and fabrication of Tonpilz type acoustic transducer using grain oriented Tb-Dy-Fe magnetostrictive material

A Tonpilz type transducer has been designed and fabricated using grain oriented Tb0.3Dy0.7Fe1.95 magnetostrictive rods as active elements. The design include provisions for DC biasing of the active elements with the help of an array of resin-bonded Nd-Fe-B ring magnets, AC drive coil and a pre-stressing mechanism. Resonance frequency of this transducer was found to be 1.6 kHz. A Transmitting Current Response (TCR) of 167 dB ref 1μPa/A at 1 m and a Transmitting Power Response (TPR) of 152 dB ref lμPa/W were achieved. The Source Level (SL) was determined to be 177 dB ref μPa at 1m.

Investigation on the Microstructure, Texture and Magnetostriction of Directionally Solidified Alloys

Effect of V addition on the microstructure and magnetostriction of directionally solidified Tb0.3Dy0.7Fe1.95 has been investigated. The microstructure of V added alloys (Tb0.3Dy0.7 with , 0.025, 0.05, and 0.075) indicate that Fe-50 at.% V is formed as primary phase, which subsequently undergoes spinodal decomposition. The spinodially decomposed Fe-rich phase reacts with the liquid and forms the matrix phase, (Tb,Dy)Fe2. The V-rich spinodally decomposed product, on the other hand, exists as remnant phase without undergoing any metallurgical transformation. Texture studies indicate that the grains of (Tb,Dy)Fe2 show /rotated and orientations for all compositions investigated in the directionally solidified condition. An improvement in magnetostriction has been noticed for small addition of V and with further addition the magnetostrictive property decreases. The formation of additional phases containing vanadium is attributed to be the reason when V is added in higher concentration levels.

Favorable Effect of Ho Addition on the Microstructure and Magnetostriction of Textured Tb0.3Dy0.7Fe1.95

This paper reports the effect of Ho on the microstructure, texture and magnetostrictive properties of Tb0.3Dy0.7-xHoxFe1.95 (with x = 0, 0.05, 0.1, 0.15 and 0.2) alloys. The alloys were vacuum induction melted and directionally solidified by modified Bridgman technique. Ho addition has been found to improve the magnetostriction at lower concentration due to absence of deleterious pro-peritectic (Tb,Dy)Fe3 phase. The static strain co-efficient is found to be better in Ho added alloys and the prevalence of strong and texture is attributed to be the reason.

Evolution of Texture during Directional Solidification of Giant Magnetostrictive Tb0.3Dy0.7Fe1.95 Alloy

The development of preferred grain orientation has been investigated in the directionally solidified samples of Tb0.3Dy0.7Fe1.95 as a function of pulling speed viz. 10, 40, 70 and 100 cm/h. The study indicates that at lower solidification rate (10 cm/h) growth of and texture components are preferred, whereas, texture component becomes dominant at higher pulling rate (100 cm/h). However, as the solidification progresses, growth of texture component is observed subduing the other components. Consequently, the magnetostriction improves from 1100 to 1350 micro-strains with higher pulling speed.

Structural And Magnetic Properties Of Dy0.7Tb0.3Fex [x = 2, 3]

Alloys of Dy0.7Tb0.3Fex [x = 2, 3] were prepared and investigated for structural and magnetic properties. A three phase microstructure consisting of (Dy,Tb)Fe2, (Dy,Tb)Fe3 and (Dy,Tb)‐rich phases were found for the alloy x = 2, whereas a two phase microstructure consisting of (Dy,Tb)Fe3 and (Dy,Tb)6Fe23 was found for the alloy x = 3. The saturation magnetization, Curie temperature and the magnetostriction were found to be lower for the Fe‐rich alloy (x = 3) as compared to the alloy x = 2. The anisotropy also was found to be lower for x = 3 which explains the reason for lower magnetostriction.