Implementation of Digital Lock-in Amplifier based Transport Measurements in Pulsed High Magnetic Fields and Scaling of Thermal Hysteresis in Mn₅₀Ni₄₀Sn₁₀ Huesler Alloy

Prasad, Mithun S (2017) Implementation of Digital Lock-in Amplifier based Transport Measurements in Pulsed High Magnetic Fields and Scaling of Thermal Hysteresis in Mn₅₀Ni₄₀Sn₁₀ Huesler Alloy. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

Lock-in amplifier based electrical Measurements by limiting the bandwidth to a very narrow frequency window improve the signal to noise ratio by many orders of magnitude compared to conventional ”DC measurements”. But such measurements are usually done under quasi-static conditions where the sample physical properties change over a relatively long time scale (seconds to minutes). In pulsed high magnetic field requires the sample to be excited with very high frequencies for getting accurate measurements. Generation of very high modulating signal is one of the limitation of normal lock-in measurement. As an alternative, we have to develop digital lock-in technique which can carry out all the functions of lock-in along with processing of signal with very high frequency.Before implementing digital lock-in technique, one must check the reliability of the data which we obtain after processing. This can be done by comparing the data obtained from lock-in and digital lock-in for well studied sample. Magnetocaloric effect (MCE) is an interesting phenomena that can change the future of the world. This effect mainly arises due the magneto-structural phase transition happens in some magnetic materials. Mn rich Mn-Ni-Sn alloy shows very large MCE effect which makes it suitable candidate for magnetic refrigerant. It is always interesting to study the dynamic of phase transition happening in these materials and also look into some of their transport properties under high magnetic field.

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