Raman spectroscopy is a very powerful probe to study the nature of quasi-particle excitations in condensed matter physics. The work presented in this thesis is focused on two different families of novel materials, namely the iron-based superconductors (FeBS), multiferroic oxides and double perovskite. Although the properties of these two systems are quite different, some comparison can still be drawn between them. For instance, in both of these systems magnetism plays a crucial role and intricate coupling between phononic, magnetic and orbital degrees of freedom is crucial to understand their underlying physics responsible for their various exotic physical properties. Understanding the microscopic origin of quasi-particle excitations, such as phonons, magnons, orbitons, plasmons etc., and coupling between them in these complex materials, has been an intense field of research because it is believed that these excitations hold the key for explaining their rich physics. The systems studied in the thesis include (A) FeBS - (i) FeSe0.82 (ii) Ce1-zYzFeAsO1-xFx (z = 0, 0.4; x = 0.1, 0.2) (iii) Ca4Al2O5.7Fe2As2 (iv) Ca(Fe1-xCox)2As2 (x = 0.03, 0.05). (B) Multiferroic oxides - (i) AlFeO3 (ii) TbMnO3 and double perovskite (iii) La2NiMnO6.
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