Peculiarities of magnetic, galvanomagnetic, elastic, and magnetoelastic properties of Eu0.55Sr0.45MnO3

Abstract

Magnetic, elastic, magnetoelastic, transport, and magnetotransport properties of the Eu0.55Sr0.45MnO3 ceramics have been studied. A break was detected in the temperature dependence of electrical resistivity ρ(T) near the temperature of the magnetic phase transformation (41 K), with the material remaining an insulator down to the lowest measurement temperature reached (ρ=106 Ω cm at 4.2 K). In the interval 4.2≤T≤50 K, the isotherms of the magnetization, volume magnetostriction, and ρ were observed to undergo jumps at the critical field H C1, which decreases with increasing T. For 50≤T≤120 K, the jumps in the above curves persist, but the pattern of the curves changes and H C1 grows with increasing T. The magnetoresistance Δρ/ρ = (ρ H −ρ H=0)/ρ H is positive for H<H C1 and passes through a maximum at 41 K, where Δρ/ρ = 6%. For H>H C1, the magnetoresistance is negative, passes through a minimum near 41 K, and reaches a colossal value of 3×105 % at H=45 kOe. The volume magnetostriction is negative and attains a giant value of 4.5×10−4atH=45 kOe. The observed properties are assigned to the existence of three phases in Eu0.55Sr0.45MnO3, namely, a ferromagnetic (FM) phase, in which carriers are concentrated because of the gain in s-d exchange energy, and two antiferromagnetic (AFM) phases of the A and CE types. Their fractional volumes at low temperatures were estimated to be as follows: ∼3% of the sample volume is occupied by the FM phase; ∼67%, by the CE-type AFM phase; and ∼30%, by the A-type AFM phase.