Ultralow Voltage Manipulation of Ferromagnetism

Abstract

Spintronic elements based on spin transfer torque have emerged with potential for on-chip memory, but they suffer from large energy dissipation due to the large current densities required. In contrast, an electric-fielddriven magneto-electric storage element can operate with capacitive displacement charge and potentially reach 1-10 J cm 2 switching operation. Here, magnetoelectric switching of a magnetoresistive element is shown, operating at or below 200 mV, with a pathway to get down to 100 mV. A combination of phase detuning is utilized via isovalent La substitution and thickness scaling in multiferroic BiFeO3 to scale the switching energy density to 10 J cm 2. This work provides a template to achieve attojoule-class nonvolatile memories.

Toward Intrinsic Ferroelectric Switching in Multiferroic BiFeO3

“…As observed, the LBFO consistently switches faster than its BFO counterpart. Within the BFO system, it has been shown experimentally that lanthanum substitution reduces the rhombohedral distortion thereby lowering the magnitude of the remnant polarization and the coercive field [25,26]. Similarly, density-functional-theory calculations show that lanthanum substitution reduces both the potential-energy barrier between, and magnitude of, the degenerate ground states of polarization [25,26].…”

Large Tunnel Electroresistance with Ultrathin Hf0.5Zr0.5O2 Ferroelectric Tunnel Barriers

“…High density, high‐speed, and low power consuming nonvolatile memories are currently being vigorously explored for use in next‐generation computation, particularly due to the performance gap between the logic and memory elements of the current computational architecture. [ 1–3 ] Of various explored material systems, electrically switchable spontaneous polarization of ferroelectric materials enables a robust nonvolatile memory solution. [ 4–6 ] One such promising memory element is the ferroelectric tunnel junction (FTJ), which, unlike ferroelectric RAM, offers nondestructive readout, in addition to low operation energy and high operation speed.…”

Electric field control of magnetism: multiferroics and magnetoelectrics

“…Efforts in this direction are currently being undertaken. For example, magnetoelectric switching of a magnetoresistive element was recently shown to operate at or below 500 mV, with a pathway to get down to 100 mV [136]. A combination of phase detuning is utilized via isovalent lanthanum substitution and thickness scaling in BiFeO 3 to scale the switching energy density to ≈ 10 µJ cm −2 .…”

“…They key to this work was leveraging effects of lanthanum substitution which is known to both lower the polarization and the ordering temperature (and therefore the energy of switching) of the ferroelectric and to take advantage of innate thickness scaling effects (thinner films require smaller voltages for switching). In turn, the researchers showed that the switching voltage of the giant magnetoresistance (GMR) response can be progressively reduced from ≈ 1 V to ; c is the corresponding piezoelectric phase data showing switching of the polar state at~500 mV for the 20 nm LBFO layer; also shown are the corresponding XMCD-PEEM (at the Co-edge) for a CoFe dot that has been switched (from BLACK to WHITE) with a bias of 500 mV; d is the corresponding XMCD-PEEM data for a CoFe dot on a 10 nm LBFO layer showing switching at~200 mV [136] 500 mV by a reduction of the film thickness down to 20 nm (Fig. 21a).…”