Effect of isoelectronic substitution on magnetic properties of Ni2Mn(GaB) Heusler alloys

• Published in: Journal of physics. Condensed matter 2008-11, Vol.20 (46), p.465209-465209 (5)
• Main Authors: Gautam, Bhoj Raj, Dubenko, Igor, Pathak, Arjun Kumar, Stadler, Shane, Ali, Naushad
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Domain effects, magnetization curves, and hysteresis; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Magnetic properties and materials; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Physics; Solid-solid transitions; Specific phase transitions
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/20/46/465209

We have studied the structural and magnetic properties of Ni2MnGa1-xBx Heusler alloys with 0 < =x < =0.25 using x-ray diffraction, thermal expansion, electrical resistivity, and magnetization measurements. The magnetization measurements were made within the temperature interval of 5-400 K and at applied magnetic field of 0-5 T. The samples with low B concentrations (x < 0.05) were found to be of the cubic L21 phase at 300 K. A martensitic phase along with the cubic L21 phase appears for x > =0.05, and the amount of the martensitic phase was found to increase with increasing x. The critical concentration of the boron substitution (within which Heusler phases exist) was found to be around x = 0.1. The cubic cell parameter was observed to decrease with increasing x in the interval 0 < =x < =0.1. The alloys were ferromagnetically ordered at 5 K and the saturation magnetization (MS) was found to decrease with increasing boron concentration. The Curie temperatures (TC) and martensitic transition temperatures (TM) for the alloys with 0 < =x < =0.25 have been determined and a phase (T-x) diagram has been constructed. TM increases rapidly and TC decreases slowly with increasing B concentration in the interval 0 < =x < =0.1. The dependence of the phase transition temperatures and magnetization on B concentration is discussed.