[PDF][PDF] Magnetoelectric effects in complex oxides with competing ground states

HJA Molegraaf, J Hoffman, CAF Vaz, S Gariglio… - Adv …, 2009 - dirkvandermarel.ch
HJA Molegraaf, J Hoffman, CAF Vaz, S Gariglio, D van der Marel, CH Ahn, JM Triscone
Adv. Mater, 2009dirkvandermarel.ch
The drive to develop materials with new multifunctional capabilities has rekindled interest in
multiferroics—systems which are characterized by the simultaneous presence of, and
coupling between, magnetic and electric order parameters. In naturally occurring
multiferroics the magnetoelectric coupling is often weak, and new classes of artificially
structured composite materials that combine dissimilar magnetic and ferroelectric systems
are being developed to optimize order parameter coupling.[1–6] Here, we describe direct …
The drive to develop materials with new multifunctional capabilities has rekindled interest in multiferroics—systems which are characterized by the simultaneous presence of, and coupling between, magnetic and electric order parameters. In naturally occurring multiferroics the magnetoelectric coupling is often weak, and new classes of artificially structured composite materials that combine dissimilar magnetic and ferroelectric systems are being developed to optimize order parameter coupling.[1–6] Here, we describe direct, charge-mediated magnetoelectric coupling in a heterogeneous multiferroic that takes advantage of the sensitivity of a strongly correlated magnetic system to competing electronic ground states. Using magneto-optic Kerr effect magnetometry, we observe large magnetoelectric coupling in ferroelectric/lanthanum manganite heterostructures, including electric field-controlled on/off switching of magnetism. These results open a new vista for the development of novel magnetoelectric devices with large charge coupling between electric and magnetic degrees of freedom. Doped lanthanum manganites are complex oxides characterized by a strong interplay between electron transport, magnetism, and crystal lattice distortions, leading to a rich variety of electronic behavior, including magnetic and charge-ordered states, colossal magnetoresistance (CMR), and a diversity of electron transport behavior. Underlying the competition between these ground states is the prominent role of charge in double exchange, hopping, and orbital overlap.[7, 8] To date, controlling charge as a parameter has most often been achieved using chemical doping, which is robust, and permanent. An alternative approach to modulate carrier density is to use an electrostatic field,[9–15] which has been used successfully to modulate charge-dependent phenomena, including superconductivity [16] and dilute magnetic semiconducting behavior.[12, 13, 17] In these systems, the nature of the electron correlations results in a strong sensitivity of the material properties to the charge-carrier concentration. Magnetism has also been controlled at interfaces using field effects. Magnetotransport measurements (planar and anomalous Hall effect, magnetoresistance, resistance) indicate large changes in critical temperature,[12, 13, 18–20] while changes in coercivity have also been observed.[14] Moreover, magnetoelectric effects at interfaces have been predicted to arise from spin density accumulation in metallic ferromagnet/ferroelectric structures, induced by charge screening of the electric field.[5] These experimental and theoretical results point to the potential of these types of structures for nanostructured multiferroics. Here, we demonstrate a large charge-driven magnetoelectric coupling effect in a Sr-doped lanthanum manganite/ferroelectric composite structure resulting from direct control of magnetism via charge carrier density. This approach has the advantage that its physical mechanism is transparent and the size of the effect can be quantified and understood qualitatively within the double exchange model, in particular the observed variation of the magnetic moment and critical temperature with charge carrier concentration. This approach is an alternative to electroelastic modulation of the magnetic properties of magnetic/ferroelectric composites, where magnetoelectric coupling is achieved through changes in magnetic anisotropy and remanent magnetization via strain.[1, 21] The converse effect, in which the electric polarization is modulated by a magnetic field, has also been demonstrated.[1, 2, 22, 23]
In this study, we use off-axis magnetron sputtering to grow a continuous 250 …
dirkvandermarel.ch
以上显示的是最相近的搜索结果。 查看全部搜索结果