Phase Formation, Magnetostructural Transition And Magnetocaloric Properties In Off-Stoichiometric Ni-Mn-Z (Z = Ga, Sn)Heusler Alloys.: The Present Research Work Reports Experiential Studies On The Phase Formation, Magnetostructural And Magnetocaloric Properties Of A Novel Series Of Ferromagnetic Shape Memory Materials Of Off-Stoichiometric Heusler Alloys Ni-Mn-Z (Z = Ga, Sn) In Forms Of Ingots And Thin Ribbons. The Aim Is Two Fold; One From The Applied Point Of View And The Other From Fundamental Aspects. In The Application Part, The Main Objective Is To Develop A Magnetic Refrigerant With Large Magnetocaloric Properties Near Room Temperature, Whereas In The Other Part, The Motive Is To Develop Basic Understanding Of Underlying Processes Of The Structural, Thermomagnetic, Magneto-Transport And Magnetocaloric Properties In Correlation To The Microstructure. The Ni And Ga Rich Alloys In The Ni-Mn-Ga System And Mn Rich Alloys In The Ni-Mn-Sn System Are Chosen In View Of Tuning The Martensite Transition With Optimal Magnetocaloric Properties Near Room Temperature. A Partial Ni → Mn Substitution In The Ni-Rich Ni50+Xmn25-Xga25 (X≤5) Series Promotes The Martensite Phase Stabilization Near Room Temperature. In The Other Series Ni55mn20-Yga25+Y, A Small Ga → Mn Substitution (Y≤2) Leads To Trigger A Single Magnetostructural Transition With Functional Magnetocaloric Properties. An Advantage With The Ni50mn50-Zsnz (Z =11.5-15.0) Alloy Series Is That It Yields Inverse Magnetocaloric Properties Near Room Temperature. The Results Of The Structural (In Terms Of X-Ray Diffraction And Microstructure), Thermal, And Magnetocaloric Properties Obtained On These Three Alloy Series Under Selective Experimental Conditions Are Presented In Five Different Chapters 3-7. Chapter-1 Gives A General Introduction About The Subject Of Ferromagnetic Heusler Alloys, With The Statement Of The Problem, Review Of The Literature Along With The Motivation Behind Selecting This Specific Class Of The Work, And Typical Physical Properties And Applications Of Such Alloys. Chapter 2 Describes Experimental Details Of The Alloy Formation And Sample Preparations In Part Of The Measurements And Analysis Of The Different Properties. Chapters 3 And 4 Deal With The Structural Transformation And The Magnetocaloric Properties Of The Ni50+Xmn25- Xga25 (X≤5) And Ni55mn20-Yga25+Y (Y≤2.0) Alloys. As Large Magnetic Entropy Change As (-) 7.0 Jkg-1k-1 Has Been Obtained In The Second Alloy Series (Y = 0.5) At 332 K. The Orderdisorder Transformation In Ni55mn20-Yga25+Y (Y = 0,1 2) Alloys In Order To Examine The A2 (Fully Disordered) → B2 (Partially Ordered) → L21 (Fully Ordered) Phase Sequence In Correlation To The Thermoelastic Caloric Properties In The Martensite Transition Are Described In Terms Of Thermal Analysis In Chapter 5. Chapters 6 And 7 Describe The Structural And Magnetic Transformation With Inverse Magnetocaloric Properties In Ni50mn50-Zsnz (Z = 11.5- 15.0) Alloys In Form Of Bulk Ingots And Ribbons, Respectively. It Is Found That The Ribbons Are Highly Sensitive In Tailoring Useful Properties For Applications. An Optimal Value Of The Refrigeration Capacity Of 22.7 Jkg-1 Thus Has Been Obtained In The Ribbons. A Summary Of The