Interrelation between electronic structure and interatomic distances for RMn2X2 compounds

The heat capacity was studied for LaMn2Si2, La0.75Y0.25Mn2Si2, La0.7Y0.3Mn2Si2, YMn2Si2 and LaFe2Si2 isostructural intermetallic compounds in the temperature range 1.8-360K. The electronic, magnetic and lattice contributions to the heat capacity of the compounds were determined and analyzed. The interrelation was found between values of the electronic contribution to the heat capacity (density of states at the Fermi level) and crystal lattice parameters of R(Mn,Fe,Ni)2Si2 compounds. The electronic contribution and the density of states at Fermi level increase with increasing lattice parameters of the compounds. The change of interlayer Mn-Mn exchange interactions with change of Y concentration in La1-xYxMn2Si2 compounds is not accompanied by considerable changes in the electronic contribution to the heat capacity and density of states at the Fermi level. The performed analysis of the magnetic contribution shows that no essential differences exist between the behavior of the heat capacity of the compounds with dMn-Mn>=dc and with dMn-Mn<dc upon various types of the magnetic phase transitions