Sa Tu

Short-Wavelength Spin Waves in Yttrium Iron Garnet Micro-Channels on Silicon

Yttrium iron garnet (YIG) has been widely used in spin wave studies thanks to its low Gilbert damping constant. However, most high-quality YIG films are grown on gadolinium gallium garnet (GGG) substrate, which makes it difficult to integrate with existing semiconductor technology. We show spin wave excitation in a nanometer-thick YIG micro-channel on silicon substrate. The YIG is grown by pulsed laser deposition (PLD) in high-purity oxygen followed by rapid thermal annealing at 800°C after deposition. Using meander coplanar waveguides at submicrometer scale, spin waves with wavelength down to 1 μm are excited. By measuring the linewidth of the spin wave reflection spectra, a Gilbert damping constant α = 1.9×10-3 was obtained.

Anomalous Nernst effect in Ir22Mn78/Co20Fe60B20/MgO layers with perpendicular magnetic anisotropy

The anomalous Nernst effect in a perpendicularly magnetized Ir22Mn78/Co20Fe60B20/MgO thin film is measured using well-defined in-plane temperature gradients. The anomalous Nernst coefficient reaches 1.8 μV/K at room temperature, which is almost 50 times larger than that of a Ta/Co20Fe60B20/MgO thin film with perpendicular magnetic anisotropy. The anomalous Nernst and anomalous Hall results in different sample structures revealing that the large Nernst coefficient of the Ir22Mn78/Co20Fe60B20/MgO thin film is related to the interface between CoFeB and IrMn.

Spin wave based synapse and neuron for ultra low power neuromorphic computation system

In this work, we have proposed that the neural synapses and neurons can be realized by utilizing spin waves (SWs) as information carrier. The SWs is excited by spin torque nano-oscillator (STNO), and detected with several different physical mechanisms: 1) tunneling magnetic-resistance 2) spin pumping and 3) inverse spin hall effect. The proposed SWs based synapses and neurons can be further combined together to form a neuromorphic computation system with crossbar structure. Possible ultra low power consumption and ultra high speed are the advantage of our proposed SWs based synapses and neurons.

Band structure calculation of thin film YIG based magnonic crystal

Magnonic Crystals (MCs) are a new class of magnetic nanostructures. The periodic modulation of at least one ferromagnetic material can be seen as a MC. In general, MCs can be divided in thin film magnonic crystals and bulk magnonic crystals, while every of these two classes can be subdivided in 1, 2 and 3 dimensional magnonic crystals. Bulk MCs were used in an early stage for theoretical studying. While neglecting effects of the external shape, they are systems which helped to lead up simple and analytical models. On the other hand thin film MCs can be used to study band information mechanisms. In analogue way to photonic crystals, MCs also have the opportunity to show a band structure with allowed minibands and forbidden bandgaps. For photonic crystals this led to photonic circuits and for MCs this can lead to new applications like spin filters, where the forbidden frequency gaps of the MCs could be used to eliminate specific frequencies of spin waves.