Magnetic ordering in Sc2CoSi2-type R2FeSi2 (R=Gd, Tb) and R2CoSi2 (R=Y, Gd-Er) compounds

Magnetic andmagnetocaloricpropertiesofSc2CoSi2-type R2TSi2 (R¼Gd-Er, T¼Fe, Co)compoundshave been studiedusingmagnetizationdata.Theseindicatethepresenceofmixedferromagneticandanti- ferromagnetic interactionsinthesecompounds.Oneobservesaferromagnetictransitionfollowedbyan antiferromagnetic orderandafurtherpossiblespin-reorientationtransitionatlowtemperatures. Compared toGd2{Fe, Co}Si2, theTb2FeSi2 and {Tb-Er}2CoSi2 compounds exhibitremarkablehysteresis (for e.g.Tb2FeSi2 showsresidualmagnetization Mres/Tb¼2.45 ?B, coercive field Hcoer¼14.9kOe,and critical field Hcrit5 kOeat5K)possiblyduetothemagnetocrystallineanisotropyoftherareearth.The R2{Fe, Co}Si2 show relativelysmallmagnetocaloriceffect(i.e.isothermalmagneticentropychange, ?Sm) around themagnetictransitiontemperature:themaximalvalueofMCEisdemonstratedbyHo2CoSi2 (?Sm¼8.1J/kgKat72Kand ?Sm¼9.4 J/kgKat23Kin field changeof50kOe)andEr2CoSi2 (?Sm ¼13.6J/kgKat32Kand ?Sm¼8.4 J/kgKat12Kin field changeof50kOe)