Thermal Control of the Magnon-Photon Coupling in a Notch Filter coupled to a Yttrium-Iron-Garnet/Platinum System

We report thermal control of mode hybridization between the ferromagnetic resonance (FMR) and a planar resonator (notch filter) working at 4.74 GHz. The chosen magnetic material is a ferrimagnetic insulator (Yttrium Iron Garnet: YIG) covered by 6 nm of platinum (Pt). A current induced heating method has been used in order to enhance the temperature of the YIG/Pt system. The device permits us to control the transmission spectra and the magnon-photon coupling strength at room temperature. These experimental findings reveal potentially applicable tunable microwave filtering function.Comment: 5 pages, 4 figure

Epitaxial growth, structural characterization and exchange bias of non-collinear antiferromagnetic Mn3_{3}Ir thin films

Antiferromagnetic materials are of great interest for spintronics. Here we present a comprehensive study of the growth, structural characterization, and resulting magnetic properties of thin films of the non-collinear antiferromagnet Mn$_{3}$Ir. Using epitaxial engineering on MgO (001) and Al$_{2}$O$_{3}$ (0001) single crystal substrates, we control the growth of cubic ${\gamma}$-Mn$_{3}$Ir in both (001) and (111) crystal orientations, and discuss the optimization of growth conditions to achieve high-quality crystal structures with low surface roughness. Exchange bias is studied in bilayers, with exchange bias fields as large as -29 mT (equivalent to a unidirectional anisotropy constant of 11.5 nJ cm$^{-2}$) measured in Mn$_{3}$Ir (111) / permalloy heterostructures at room temperature. In addition, a distinct dependence of blocking temperature on in-plane crystallographic direction in Mn$_{3}$Ir (001) / Py bilayers is observed. These findings are discussed in the context of chiral antiferromagnetic domain structures, and will inform progress towards topological antiferromagnetic spintronic devices.Comment: 15 pages, 10 figure

THERMAL CONTROL OF THE MAGNON-PHOTON COUPLING IN A NOTCH FILTER COUPLED TO A YIG/Pt SYSTEM

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Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature.

Highly efficient current-induced motion of chiral domain walls was recently demonstrated in synthetic antiferromagnetic (SAF) structures due to an exchange coupling torque (ECT). The ECT derives from the antiferromagnetic exchange coupling through a ruthenium spacer layer between the two perpendicularly magnetized layers that comprise the SAF. Here we report that the same ECT mechanism applies to ferrimagnetic bi-layers formed from adjacent Co and Gd layers. In particular, we show that the ECT is maximized at the temperature TA where the Co and Gd angular momenta balance each other, rather than at their magnetization compensation temperature TM. The current induced velocity of the domain walls is highly sensitive to longitudinal magnetic fields but we show that this not the case near TA. Our studies provide new insight into the ECT mechanism for ferrimagnetic systems. The high efficiency of the ECT makes it important for advanced domain wall based spintronic devices

Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature.

Highly efficient current-induced motion of chiral domain walls was recently demonstrated in synthetic antiferromagnetic (SAF) structures due to an exchange coupling torque (ECT). The ECT derives from the antiferromagnetic exchange coupling through a ruthenium spacer layer between the two perpendicularly magnetized layers that comprise the SAF. Here we report that the same ECT mechanism applies to ferrimagnetic bi-layers formed from adjacent Co and Gd layers. In particular, we show that the ECT is maximized at the temperature TA where the Co and Gd angular momenta balance each other, rather than at their magnetization compensation temperature TM. The current induced velocity of the domain walls is highly sensitive to longitudinal magnetic fields but we show that this not the case near TA. Our studies provide new insight into the ECT mechanism for ferrimagnetic systems. The high efficiency of the ECT makes it important for advanced domain wall based spintronic devices

Magnetic and electrical transport signatures of uncompensated moments in epitaxial thin films of the noncollinear antiferromagnet Mn3Ir

Noncollinear antiferromagnets, with either an L1(2) cubic crystal lattice (e.g., Mn3Ir and Mn3Pt) or a D0(19) hexagonal structure (e.g., Mn3Sn and Mn3Ge), exhibit a number of phenomena of interest to topological spintronics. Among the cubic systems, for example, tetragonally distorted Mn3Pt exhibits an intrinsic anomalous Hall effect (AHE). However, Mn3Pt only enters a noncollinear magnetic phase close to the stoichiometric composition and at suitably large thicknesses. Therefore, we turn our attention to Mn3Ir, the material of choice for use in exchange bias heterostructures. In this letter, we investigate the magnetic and electrical transport properties of epitaxially grown, face-centered-cubic gamma-Mn3Ir thin films with (111) crystal orientation. Relaxed films of 10 nm thickness exhibit an ordinary Hall effect, with a hole-type carrier concentration of (1.500 +/- 0.002) x 10(23) cm(-3). On the other hand, TEM characterization demonstrates that ultrathin 3 nm films grow with significant in-plane tensile strain. This may explain a small net magnetic moment, observed at low temperatures, shown by X-ray magnetic circular dichroism spectroscopy to arise from uncompensated Mn spins. Being of the order of 0.02 mu(B)/atom, this dominates electrical transport behavior, leading to a small AHE and negative magnetoresistance. These results are discussed in terms of crystal microstructure and chiral domain behavior, with spatially resolved XML(C)D-PEEM supporting the conclusion that small antiferromagnetic domains, <20nm in size, with differing chirality account for the absence of observed Berry curvature driven magnetotransport effects. Published under license by AIP Publishing