Sm1−xSrxMnO3 manganites: unusual magnetic, electric and elastic properties dueto phase separation

Abstract

Colossal magnetoresistance (CMR) (Δρ/ρ)and giant negative volume magnetostriction (ω) havebeen observed in the Curie temperature region of Sm1−xSrxMnO3 manganites, for x = 0.33 compoundscontaining ferromagnetic (FM) and A-type antiferromagnetic (AFM) clusters and for x = 0.4, 0.45 compoundscontaining FM and both types of AFM clusters (A-type and charge-ordering (CO) type). For x = 0.33, the magnetizationσ, Δρ/ρand ωincrease smoothly with magnetic field increase and saturation of Δρ/ρ and ω is not achieved.Isotherms of σ,Δρ/ρand ωfor x = 0.4and 0.45 show another behaviour: sharp jumps of σ, Δρ/ρ and ω take place at HC1 ≤H≤HC2,and saturation is achieved at H≥HC2.We consider that the reason for CMR and giant magnetostrictionbeing observed in the compounds investigated is the increase of theFM phase volume under the action of the magnetic field. For x = 0.33 this increaseis smooth because it arises from FM phase ‘sprouting’ on FM layers of A-type AFM phase.For x = 0.4and 0.45 the increase of the volume of the FM part arises from CO clusters withCE-type AFM structure too. In this case, CO clusters are completelytransformed to the FM state with a large saturation magnetization σs which is equalto ∼ 70 %of σsat T = 1.5K. This transition is accompanied by crystal structure reconstruction that ismanifested in both the temperature and magnetic field dependences of theanisotropic magnetostriction.