Abstract

The effect of optical pumping and magnetic field on properties of the electronic phase separation regions, which are the multiferroic semiconductor heterostructures in the form of superlattices, have been studied in Eu0.8Ce0.2Mn2O5. These superlattices are formed due to self-organization in a dielectric crystal matrix as a result of the competing internal interactions balance and occupy a small crystal volume. The dynamical equilibrium states of superlattices are initially formed during cycling of as-grown samples in a magnetic field. The superlattices in such states are ferromagnetic and electrically neutral. Sets of ferromagnetic resonances were observed from individual layers of superlattices. Their features give rise information on properties of these layers and of a superlattice as a whole. The differences in the parameters of these resonances were due to different distributions of Mn3+ and Mn4+ ions in individual superlattices layers. It has been found that optical pumping having different powers allows us to control of multiferroic properties of superlattices layers by changing their magnetic and electric properties. It is shown that, under certain conditions, it is possible to significantly increase the temperatures at which multiferroic heterostructures exist.

Highlights

  • Multiferroics RMn2 O5 (R are rare-earth ions, Bi) belong to type II multiferroics, in which ferroelectric ordering below the Curie temperature (TC ≈ 30–35 K) is induced by magnetic ordering with the Néel temperature (TN ≈ 35–40 K) [1,2]

  • A characteristic feature of RMn2 O5 is the presence of an equal number of Mn3+ ions and Mn4+ ions, which provides conditions for charge ordering at a dielectric state

  • Before discussing the effect of optical pumping at various powers on properties of Eu0.8 Ce0.2 Mn2 O5 (ECMO) superlattices layers in the dynamically equilibrated states, let us consider the effect of temperature and magnetic field changes on the properties of such superlattices without of pumping

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Summary

Objects and Research Methods

Single crystals of ECMO were grown by spontaneous crystallization from a solutionmelt [26,27]. Pairs and the concentration of superlattices were increased As before, these superlattices occupied a small crystal volume in ECMO [10,13]. Some of the Eu3+ ions were replaced by larger Ce3+ ions (though with a lower probability) These ions contained lone pairs of 6s2 electrons on the outer shells. Optical pumping was performed by a solid-state pulsed neodymium laser LTIPCH-8 with a simultaneous generation of the first (1.06 μm) and second (532 nm) harmonics. In this case, formation of excitons in the Mn ions subsystem occurred by the optimal way [31]

Experimental Data and Analysis
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