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In this paper, the crystal morphology and grain size evolution of Ge–Sb–Te (GST) irradiated by multi-pulsed picosecond (ps) laser were characterized by transmission electron microscopy and selected area electron diffraction. Morphologies induced by multi-pulsed laser were radially quasiperiodic structures, and the crystallization area induced by the first laser pulse acted as the periodic repeated unit. Single laser pulse irradiation produced three different conterminal annular crystallization zones, and their formation mechanisms were discussed. GST films accumulated thermal and structural change induced by per laser pulse, reducing crystallization threshold and extending crystallization fluence range. Sequentially, every subsequent laser pulse created a new crystallization area, and then accumulated to be a pulse number dependence radially quasiperiodic structure. Meanwhile, the laser pulse train dramatically refined grains. The grain boundaries are presented as an alternating-layered structure or atomic ordering domain. The present study revealed microstructure evolution of intermediate states for multi-level storage and realized multi-phase changes and is critical to enhance storage density.

Magnetic/piezoelectric multiferroic heterostructures with strong magnetoelectric (ME) coupling have recently attracted considerable interest. Since the ratio of magnetostriction ?s over saturation magnetization Ms is a key factor to achieve strong magnetoelectric coupling in ferrite/piezoelectric multiferroic heterostructures, here we find a solution to tune ?s/Ms by aluminum doping. We report aluminum-substituted NiZn-ferrites with different compositions (Ni0.65Zn0.35Fe2?xAlxO4, x?=?0, 0.1, 0.3, 0.4, 0.6, 0.8 and 1) fabricated by a solid-state sintering process. The saturation magnetization of these NiZnAl-ferrites was reduced from 6000 to 900?G with increased Al doping, which was accompanied by a significantly narrowed ferromagnetic resonance linewidth from 1870 to 340?Oe. Meanwhile, saturation magnetostriction of these NiZnAl-ferrites was reduced from 6.67 to 1.40?ppm with increased amount of Al doping. Strong ME coupling was demonstrated in the NiZnAl-ferrites/PZT multiferroic heterostructures. A large piezoelectric deformation induced ferromagnetic resonance field change up to 42?Oe was observed in Ni0.65Zn0.35Fe1.2Al0.8O4/PZT heterostructures, corresponding to a large microwave ME coefficient of 4.2?Oe?cm?kV?1. These AlNiZn-ferrites and NiZnAl-ferrites/PZT heterostructures with large ME coupling provide a great opportunity for electrical tuning microwave devices.

Strong magnetoelectric (ME) interaction was demonstrated at both dc and microwave frequencies in a novel Zn0.1Fe2.9O4/PMN‐PT (lead magnesium niobate‐lead titanate) multiferroic heterostructure, which was prepared by spin-spray depositing a Zn0.1Fe2.9O4 film on a single-crystal PMN‐PT substrate at a low temperature of 90 ◦ C. A large electric-field induced ferromagnetic resonance field shift up to 140Oe was observed, corresponding to an ME coefficient of 23OecmkV −1 . In addition, a large electrostatic field tuning of the magnetic hysteresis loops was observed with a large squareness ratio change of 18%. The spin-spray deposited ferrite/piezoelectric multiferroic heterostructures exhibiting strong ME interactions at both dc and microwave frequencies provide great opportunities for novel electrostatically tunable microwave magnetic devices synthesized at a low temperature. (Some figures in this article are in colour only in the electronic version)