The voltage impulse-induced large, nonvolatile, and tunable magnetization switching in a Ni80Co20/Pb(Mg, Nb)O3-PbTiO3 (PMN-PT) structure was investigated at room temperature. Ni80Co20 was deposited onto a specified PMN-PT substrate with defect dipoles. By exploiting defect dipoles, a distinct and stable strain memory state was achieved at zero electric field. It induces and sustains two distinct magnetization states when removing an electric field via the magnetoelectric coupling effect. Via the detailed x-ray diffraction and piezoresponse force microscopy analyses, the polarization switching pathway and the lattice strain in response to the in situ electric field were investigated to understand the microscopic mechanisms behind the nonvolatile magnetic memory. Furthermore, the impulse electric field can be selected in the range between the coercive field and the saturation field of the PMN-PT, leading to a wide range controlling technique. This work provides a promising way to produce a large and nonvolatile magnetic memory in magnetoelectric heterostructure and is significant for ultra-low-power information storage devices.
An energy efficient technique has shown to produce a three-state magnetic memory cell in a [011]-poled Ni80Co20/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) heterostructure. Via the magnetic field deposition, a 45° magnetic easy axis of the NiCo film was induced in the film plane. By using a strong converse magnetoelectric coupling between the NiCo film and the PMN-PT, the magnetic moments of NiCo can be modulated to [001] and [1-10] directions of PMN-PT by selecting an appropriate electric field (E-field). Consequently, large, medium, and small anisotropic magnetoresistance (AMR) values are obtained by fixing a measuring current along the [001] direction. The required E-field significantly reduces due to the initial direction of NiCo along the 45° direction. The tunability of the AMR ratio is as large as ∼87%. These results indicate that an energy efficient approach to generate magnetic storage by using only a small E-field rather than a magnetic field with a high energy consumption was realized. This work shows great potential for the development of ultra-low power and high-density magnetoresistive memory devices.
Pure voltage-controlled magnetism, rather than a spin current or magnetic field, is the goal for next-generation ultralow power consumption spintronic devices. To advance toward this goal, we report a voltage-controlled nonvolatile 90° magnetization rotation and voltage-assisted 180° magnetization reversal in a spin-valve multiferroic heterostructure. Here, a spin valve with a synthetic antiferromagnetic structure was grown on a (110)-cut Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrate, in which only the magnetic moment of the free layer can be manipulated by an electric field (E-field) via the strain-mediated magnetoelectric coupling effect. As a result of selecting a specified PMN-PT substrate with defect dipoles, nonvolatile and stable magnetization switching was achieved by using voltage impulses. Accordingly, a giant, reversible and nonvolatile magnetoresistance modulation was achieved without the assistance of a magnetic field. In addition, by adopting a small voltage impulse, the critical magnetic field required for complete 180° magnetization reversal of the free layer can be tremendously reduced. A magnetoresistance ratio as large as that obtained by a magnetic field or spin current under normal conditions is achieved. These results indicate that E-field-assisted energy-efficient in-plane magnetization switching is a feasible strategy. This work is significant to the development of ultralow-power magnetoresistive memory and spintronic devices.
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