Najam Ul Hassan

Title : Tunable martensitic transformation and magnetic properties of Sm doped NiMnSn ferromagnetic shape memory alloys

Abstract:

NiMnSn ferromagnetic shape memory alloys exhibit martensitic transformation at low temperature restricting from the applications. Therefore, it is a key factor to improve martensitic transformation temperature which is effectively carried out by proper element doping. In this research work, we have investigated the martensitic transformation and magnetic properties of Ni43Mn46-x SmxSn11 (x=0, 1, 2, 3) alloys on the basis of structural and magnetic measurements. X-ray diffraction shows that the crystal structure transforms from cubic L21 to orthorhombic martensite and gamma (γ) phase. The reverse martensitic and martensitic transformations are indicated by exothermic and endothermic peaks in differential scanning calorimetry. The martensitic transformation temperature increases considerably with Sm doping and goes over room temperature for Sm=3 at. %. The Ni43Mn45SmSn11 alloy exhibits magneto structural transformation, leading to large magnetocaloric effect near room temperature. The existence of thermal hysteresis and metamagnetic behavior of Ni43Mn45SmSn11 confirms the first order magneto structural transition. The magnetic entropy change reaches 20 J·kg-1·K-1 at 266 K Ni43Mn45SmSn11 and refrigeration capacity ~ 162 J.Kg-1 under magnetic field variation of 0-5 T.

What will audience learn from your presentation

• Martensitic Transformation, Magnetocaloric effect, Magnetic refrigeration.
• The materials showing martensitic transformation (MT) exhibit various multifunctional phenomena such as magnetocaloric effect (MCE), exchange bias (EB), magnetothermal conductivity (MC) and magnetoresistance (MR). This coupled transition is obtained around the MT temperature.
• The MCE is a magneto-thermodynamic phenomenon in which temperature is changed in the material when exposed to the external-non-constant magnetic field.
• Magnetic refrigeration is a best alternate conventional gas cooling technology, showing many, such as environment friendly, high refrigerant efficiency, low cast, occupying less space, low mechanical vibration, and harmlessness

Biography:

Dr. Hassan is working as Assistant Professor at Department of Physics, Division of Science & Technology, University of Education, Lahore, Pakistan. Before this he has worked as Assistant Professor of Physics at department of Physics, University of Central Punjab, Lahore, Pakistan. He has published more than 25 research papers in well-known International journals of Physics & Materials Science. He has also served as committee member, reviewer and keynote speaker in various International Conferences/Symposiums.
Dr. Hassan did his Ph.D. in Materials Science & Engineering from Nanjing University of Science & Technology, Nanjing, China. Before commencing his doctoral degree, he has worked as subject specialist in Higher Education Department, Punjab Province, Pakistan.