Magnetic order in double-layer manganites (La(1-z)Pr(z))1.2Sr1.8Mn2O7: intrinsic properties and role of the intergrowths

Abstract

We report on an investigation of the double-layer manganite series (La(1-z)Pr(z))1.2Sr1.8Mn2O7 (0 <= z <= 1), carried out on single crystals by means of both macroscopic magnetometry and local probes of magnetism (muSR, 55Mn NMR). Muons and NMR demonstrate an antiferromagnetically ordered ground state at non-ferromagnetic compositions (z >= 0.6), while more moderate Pr substitutions (0.2 <= z <= 0.4) induce a spin reorientation transition within the ferromagnetic phase. A large magnetic susceptibility is detected at {Tc,TN} < T < 250K at all compositions. From 55Mn NMR spectroscopy, such a response is unambiguously assigned to the intergrowth of a ferromagnetic pseudocubic phase (La(1-z)Pr(z))(1-x)Sr(x)MnO3, with an overall volume fraction estimated as 0.5-0.7% from magnetometry. Evidence is provided for the coupling of the magnetic moments of these inclusions with the magnetic moments of the surrounding (La(1-z)Pr(z))1.2Sr1.8Mn2O7 phase, as in the case of finely dispersed impurities. We argue that the ubiquitous intergrowth phase may play a role in the marked first-order character of the magnetic transition and the metamagnetic properties above Tc reported for double-layer manganites.

arXiv comment11 pages, 9 figures. Submitted to Phys. Rev. B

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• Bilayer manganites: polarons in the midst of a metallic breakdown
• Temperature and Field Dependence of Magnetic Domains in La${}_{1.2}$Sr${}_{1.8}$Mn${}_2$O${}_7$
• muSR Investigation of magnetically ordered states in A-site ordered perovskite manganites RBaMn2O6 (R = Y and La)