Field and temperature induced colossal strain in Gd5(SixGe1-x)4

Gd5(SixGe1-x)4, known for its giant magnetocaloric effect, also exhibits a colossal strain of the order of 10,000 ppm for a single crystal near its coupled first-order magnetic-structural phase transition, which occurs near room temperature for the compositions 0.41≤x≤0.575. Such colossal strain can be utilised for both magnetic sensor and actuator applications. In this study, various measurements have been carried out on strain as a function of magnetic field strength and as a function of temperature on single crystal Gd5Si2Ge2 (x=0.5), and polycrystalline Gd5Si1.95Ge2.05 (x=0.487) and Gd5Si2.09Ge1.91 (x=0.52). Additionally a giant magnetostriction/thermally induced strain of the order of 1800 ppm in polycrystalline Gd5Si2.09Ge1.91 was observed at its first order phase transition on varying temperature using a Peltier cell without the use of bulky equipment such as cryostat or superconducting magnet. - Research highlights: →Investigated magnetocaloric materials for magnetic refrigerator and other device applications. →Investigated the first and second order phase transition and developed an advanced technique to determine the transition temperatures. →Investigated irreversible increase in resistivity in Gd5(SixGe1-x)4 due to cycling through the phase transition. →Developed and tested a model on resistivity recovery in Gd5(SixGe1-x)4. →Investigated magnetostriction at first order phase transition for device applications.