A novel monolithic multilayered ferrimagnetic– ferroelectric multiferroic heterostructure shows a remarkably large tuning of the magnetic response with an electric field. The heteroepitaxial stack is comprised of a near single crystal yttrium iron garnet (YIG) layer, a ferroelectric barium strontium titanate (BSTO) layer with good electric field tunability, and embedded platinum (Pt) electrodes.

). Das, J.; Gao, J.; Xing, Z.; et al., "Enhancement in the field sensitivity of magnetoelectric laminate heterostructures," Appl. Phys. Lett. 95, 092501 (2009); http:// dx

Ferromagnetic resonance ͑FMR͒ derivative linewidths were measured from 3 to 12 GHz on 50 nm thick sputtered polycrystalline Fe-Ti-N films with 3 at. % titanium and a nitrogen content ͑x N ͒ from 1.9 to 12.7 at. %. The measurements were made with both stripline and waveguide FMR spectrometers. Linewidths were generally lowest at x N = 7 at. %, with derivative linewidth ͑⌬H͒ values in the 15-25 Oe range and a nominally linear increase with frequency ͑f͒. This minimum linewidth composition is connected with the bcc to bct structural transition in the Fe-Ti-N system. Linewidths increased at both larger and smaller x N values and were accompanied by the development of a more rounded frequency profile that is indicative of two-magnon scattering. All of the ⌬H vs f data could be fitted successfully with a constant inhomogeneity broadening linewidth of 8 -11 Oe, a two-magnon scattering ͑TMS͒ linewidth from the random grain-to-grain fluctuations in the effective anisotropy field directions for the polycrystal, and a magnon-electron ͑m-e͒ intrinsic relaxation term modeled through Gilbert damping with a single ␣ value of 0.003. The actual fits were done through the convolution of a Gaussian linewidth for the inhomogeneity term and a Lorentzian linewidth for the TMS and m-e terms. The fitted anisotropy field parameters from the TMS analysis ranged between 398 and 883 Oe, with the minimum also at the bcc to bct structural transition at x N = 7 at. %.

The magnetization ( M ) as a function of temperature ( T ) from 2 to 300 K and in-plane field ( H ) up to 1 kOe, room temperature easy and hard direction in-plane field hysteresis loops for fields between 100 ± Oe, and 10 GHz ferromagnetic resonance (FMR) profiles have been measured for a series of soft-magnetic nano-crystalline 50 nm thick Fe-Ti-N films made by magnetron sputtering in an in-plane field. The nominal titanium concentration was 3 at. % and the nitrogen concentrations ( N x ) ranged from zero to 12.7 at. %. The saturation magnetization ( s M ) vs. T data and the extracted exchange parameters as a function of N x are consistent with a lattice expansion due to the addition of interstitial nitrogen in the body-centered-cubic (bcc) lattice and a structural transition to body-centered-tetragonal (bct) in the 6 8 − at. % nitrogen range.

We present a comparison of the magnetoelectric (ME) response and magnetic-field sensitivities of engineered laminate sensors comprised of magnetostrictive and piezoelectric phases. The ME voltage coefficients for Metglas and single crystal fibers of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) or Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZN-PT) are about 2.8 times larger than those with Metglas-Pb(Zr,Ti)O3 (PZT) ceramic ones. This results in a 1.7 times enhancement in the magnetic-field sensitivity for the structures with single crystals. Accordingly, the noise floors are about three to four times lower for composites with PMN-PT or PZN-PT fibers than those with PZT.

Oriented barium ferrite ͑BaM͒ and polycrystalline ferroelectric barium strontium titanate ͑BSTO͒ layered structures have been fabricated by pulsed laser deposition. The 0.5 m thick BaM layer has a saturation induction of 4 kG, a uniaxial effective anisotropy field of 16 kOe, and a relatively low ferromagnetic resonance linewidth of about 25 Oe, values that are indicative of a high quality film. The dielectric constant of the 0.9 m thick BSTO layer drops by a factor of 2 for an applied voltage of 3 V.

Hybrid pulse laser deposition and liquid phase epitaxy methods have been used to produce in-plane c-axis (IPCA) oriented barium ferrite (BaM) films on a-plane (112¯0) sapphire substrates with low microwave loss and a high remanence. Total thicknesses were from 5to20μm. A reasonable compromise for low loss and high remanence was reached at a thickness of 7μm, with a remanence ratio of 0.84 and a 59GHz peak-to-peak derivative linewidth of 250Oe. The 20μm thick film had a linewidth of 110Oe, one of the smallest values ever obtained for IPCA BaM films.

The effect of lamination process on the performance of Metglas/Pb(Zr,Ti)O3‐based composite magnetoelectric (ME) sensors has been studied. Improved sensor processing can lead to higher coupling between the magnetostrictive and piezoelectric phases. A higher coupling factor results in higher magnetic field sensitivity and lower equivalent magnetic noise floors. Spin‐coat/vacuum‐bag application and cure of interfacial epoxy, in addition to the use of Metglas foils with enhanced magnetostriction (λ = 42 ppm), has led to an increase in the ME coefficient from 6 to 21.6 V/cm·Oe, and a decrease in the 1 Hz equivalent magnetic noise from 2 × 10−10 to 4 × 10−11 T/√Hz.