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Mn, Co and Ni substituted Fe3.34Ge2 hexagonal germanides were investigated through structural, Mossbauer and magnetic studies. Fe was observed to enter exclusively 2a and 2d sites of the defective structure, while vacancies only occupy the 2d site in the congruent composition. The Ge atoms were found to be slightly displaced from 2c site of the B8(sub 2) structure towards an adjacent vacancy in a 2d site. Mn and Ni exclusively enter 2a and 2d site, respectively, while Co enters both sites with a preference for 2d.

The structural and magnetic properties of the compounds NdMn2-xVxSi2 have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3-450 K. The Curie temperature and Néel temperature of layered NdMn1.9V0.1Si2 are been indicate at TC ~ 24 K and TN ~ 376 K respectively. The giant magnetocaloric effect (GMCE) around TC is found in layered NdMn1.9V0.1Si2 associated with first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd)+Fmc]. This behaviorhas been confirmed as contribution of the magnetostructural coupling by using neutron powder diffraction. The magnetic entropy change −ΔSM ~ 25.4J kg-1 K-1 and adiabatic temperature change ΔTad~ 6.7 K have been determined using magnetization and specific heat measurement under 0-8 T field applied. This compound belongs with the small thermal ~ 0.8 K and magnetic ~ 0.1 T hysteresis characteristic providing high potential material for magnetic refrigerator.

La(sub1-x)LixMnO(sub3) has been synthesized using a traditional solid sate reaction and partial melting. The compounds were of rhombohedral structure. Resistivity was measured between 4.2 K and room temperature in the magnetic fields of 0,1,2,4,8 and 13 T. Large magnetoresistance was obtained above 20-80% at fields from null to 13 T over wide temperature ranges.

Several studies are conducted to explain the temperature and magnetic field dependent neutron powder diffraction taking place in the [Ru.sub.0.9][Sr.sub.2]Y[Cu.sub.2.1O7.9] compounds. The antiferromagnetic order is shown to get destroyed with an increasing magnetic field.

The structural and magnetic properties of the re-entrant ferromagnet Pr[Mn.sub.2][Ge.sub.0.8][Si.sub.1.2] are examined. The magnetocaloric effect is measured in terms of the isothermal magnetocaloric entropy change and it is positive at the re-entrant ferromagnetic transition for a magnetic field change of 0-3 T, whereas the entropy change has become negative at the antiferromagnetic to ferromagnetic transition for the same field change.

A quaternary rare-earth intermetallic compound La3Co29Si4B10 is synthesized and the crystal and magnetic structures are investigated by neutron diffraction over the temperature range of 7-300 K. Rietveld refinements of the neutron diffraction patterns demonstrate that La3Co29Si4B10 is tetragonal and isostructural with Nd3Ni29Si4B10.

The crystal and magnetic structures of the quaternary rare-earth intermetallic compound Nd3Co29Si4B10 is investigated. Rietveld refinements of neutron-diffraction confirms that Nd3Co29Si4B10 is isostructural with Nd3Ni29Si4B10 and exhibits a canted magnetic structure below T(sub c)=200 K.

Analyzes carbon monoxide, maganese and nickle substituted Fe3.34Ge2 hexagonal germanides to perform tructural (x-ray and neutron diffraction), Mossbauer, and magnetic investigations. Methodology used to conduct the study; Information on single crystal x-ray diffraction; Details on the neutron powder diffraction; Findings of the study.