Scanning probe microscopy on ferroelectrics and ferromagnets

Abstract

This thesis deals with the investigation of exotic properties of ferroelectrics and ferromagnets newline by using scanning probe microscopy. The first part consists of the study of superconductivity newline induced in and#948; doped SrTiO3 system by laser irradiation. The second part discusses the inves newlinetigation of ferroelectricity in the CsPbBr3 perovskite system by using temperature-dependent newline Piezo Force Microscopy (PFM). And the third part discusses the fabrication and investigation newline of magnetic properties of Permalloy (Ni0.8Fe0.2) ferromagnetic nanoislands. newline SrTiO3 (STO) is known to be an incipient ferroelectric which undergoes a structural phase newline transition from a cubic to a tetragonal phase below 105K. We have used a fast laser irradiation newline technique at room temperature to modify the surface such that the low temperature tetragonal newline phase is locally created and frozen at room temperature. Upon laser irradiation, multiple do newlinemains of the tetragonal SrTiO3 form where each domain has a different long-axis direction. newline The domain boundaries are found to be highly conducting at room temperature. The irradiated newline system as a whole undergoes a superconducting transition below 150 mK. We will discuss a newline mechanism of the emergence of superconductivity in dilute electronic systems like d-doped newline STO in the light of our experiments. newline Novel ground states can also be obtained in low dimensional ferroelectric systems. We have newline investigated the ferroelectric domain structures in the nanosheets of the perovskite system newline CsPbBr3bytemperaturedependentpiezo-response force microscopy (PFM).Thedomainstruc newlineture is dependent on the temperature and the thickness of the nanosheets. Our PFM experi newlinements revealed the emergence of topological defects in the ferroelectric domains in the form of newline nanometre scale bubbles. The results raises the possibility of controlling photovoltaic effects newline in perovskite halides through ferroelectric domain imaging. newline Novel magnetic ground states can be realized in artificial lattices of magnetic nanoislands. We newline have fabric