The technological appeal of multiferroics is the ability to control magnetism with electric field. For devices to be useful, such control must be achieved at room temperature. The only single-phase multiferroic material exhibiting unambiguous magnetoelectric coupling at room temperature is BiFeO3 (refs 4 and 5). Its weak ferromagnetism arises from the canting of the antiferromagnetically aligned spins by the Dzyaloshinskii-Moriya (DM) interaction. Prior theory considered the symmetry of the thermodynamic ground state and concluded that direct 180-degree switching of the DM vector by the ferroelectric polarization was forbidden. Instead, we examined the kinetics of the switching process, something not considered previously in theoretical work. Here we show a deterministic reversal of the DM vector and canted moment using an electric field at room temperature. First-principles calculations reveal that the switching kinetics favours a two-step switching process. In each step the DM vector and polarization are coupled and 180-degree deterministic switching of magnetization hence becomes possible, in agreement with experimental observation. We exploit this switching to demonstrate energy-efficient control of a spin-valve device at room temperature. The energy per unit area required is approximately an order of magnitude less than that needed for spin-transfer torque switching. Given that the DM interaction is fundamental to single-phase multiferroics and magnetoelectrics, our results suggest ways to engineer magnetoelectric switching and tailor technologically pertinent functionality for nanometre-scale, low-energy-consumption, non-volatile magnetoelectronics.

among lung compartments, it was expected that they correlate closely. EFFi is easier to study, as it is noninvasive and may be continuously monitored. The study is limited to small groups. However, at health, the results show a low degree of variation, as expected from absence of variability caused by disease. The total separation between health and ARDS indicates that, in mechanically ventilated patients, EFFi may be useful for monitoring of ARDS evolution. This aspect is strengthened by the fact that EFFi may automatically, continuously, and noninvasively be monitored in the individual patient, who then serves as his own standard of reference. EFFi merits further studies in broad materials covering ARDS and other diseases, performed with modern capnographic equipment. n Author disclosures are available with the text of this letter at www.atsjournals.org.

Exchange coupled CoFe/BiFeO 3 thin-film heterostructures show great promise for power-efficient electric field-induced 180°magnetization switching. However, the coupling mechanism and precise qualification of the exchange coupling in CoFe/BiFeO 3 heterostructures have been elusive. Here we show direct evidence for electric field control of the magnetic state in exchange coupled CoFe/BiFeO 3 through electric field-dependent ferromagnetic resonance spectroscopy and nanoscale spatially resolved magnetic imaging. Scanning electron microscopy with polarization analysis images reveal the coupling of the magnetization in the CoFe layer to the canted moment in the BiFeO 3 layer. Electric fielddependent ferromagnetic resonance measurements quantify the exchange coupling strength and reveal that the CoFe magnetization is directly and reversibly modulated by the applied electric field through a B180°switching of the canted moment in BiFeO 3 . This constitutes an important step towards robust repeatable and non-volatile voltage-induced 180°m agnetization switching in thin-film multiferroic heterostructures and tunable RF/microwave devices.

Strain has been widely used to manipulate the properties of various kinds of materials, such as ferroelectrics, semiconductors, superconductors, magnetic materials, and “strain engineering” has become a very active field. For strain-based information storage, the non-volatile strain is very useful and highly desired. However, in most cases, the strain induced by converse piezoelectric effect is volatile. In this work, we report a non-volatile strain in the (001)-oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals and demonstrate an approach to measure the non-volatile strain. A bipolar loop-like S-E curve is revealed and a mechanism involving 109° ferroelastic domain switching is proposed. The non-volatile high and low strain states should be significant for applications in information storage.