The interfacial Dzyaloshinskii–Moriya interaction (iDMI) and the interfacial perpendicular magnetic anisotropy (iPMA) between a heavy metal and ferromagnet are investigated by employing Brillouin light scattering. With increasing thickness of the heavy-metal (Pt) layer, the iDMI and iPMA energy densities are rapidly enhanced and they saturate for a Pt thickness of 2.4 nm. Since these two individual magnetic properties show the same Pt thickness dependence, this is evidence that the iDMI and iPMA at the interface between the heavy metal and ferromagnet, the physical origin of these phenomena, are effectively enhanced upon increasing the thickness of the heavy-metal layer.
Thin film fabrication of 2D layered organic-inorganic hybrid perovskites (2D-OIHPs) for spintronic applications has been attempted using solutionbased process like Langmuir-Blodgett technique. However, monolayer or few-layered 2D magnets are not yet realized, even though a wide spectrum of 2D Ruddlesden-Popper (RP) OIHPs are known as quasi-2D Heisenberg magnets in bulk compounds. Here, chemical exfoliation by solvent engineering is applied to successfully synthesize large-sized, few unit-cell-thick 2D RP-OIHPs. Comprehensive structural characterization reveals that binary co-solvents with high relative polarity in spin coating technique are the most effective among nine kinds of solvents. Above all, this enables few-layered 2D RP-OIHP ultrathin films sustaining their intrinsic magnetic order. It is found that XY-like magnetic anisotropy driven by Jahn-Teller effect responsible for ferromagnetism in seven-layered (C 6 H 5 CH 2 CH 2 NH 3) 2 CuCl 4 ultrathin films remains very robust, whereas Ising-like dipolar anisotropy responsible for canted antiferromagnetism in ten-layered (C 6 H 5 CH 2 CH 2 NH 3) 2 MnCl 4 ultrathin films is greatly reduced. It is expected that ferromagnetism even at monolayer limit should be possible by means of further sophisticated solvent engineering as long as Jahn-Teller effect is active. The chemical exfoliation using solvent engineering unambiguously can bring about a new breakthrough in the development of 2D RP-OIHP van der Waals magnets for ultrahigh energyefficient spintronic, opto-spintronic devices.
In this study, we investigated the effect of microwave irradiation on the synthesis of ZnFe2O4 (ZFO) nanopowders. The structural, chemical, and physical features of the powders prepared via microwave-assisted heating (MWH) were analyzed with variation in the initial
precursors and synthesis temperatures. Three different types of source batches, namely Zn(CH3CO2)2 · 2H2O and FeC2O4 · 2H2O (ZAHFOH), Zn(NO3)3 · 6H2O and Fe(NO3)2
· 9H2O (ZNHFNH), and ZnO and Fe2O3 (ZOFO), were prepared. The formation of ZFO compounds was achieved at 100 °C for ZAHFOH using MWH, which is much lower than the synthesis temperature of 700 °C using conventional heating (CH). The value of the
activation energy (Q) for the ZAHFOH source in synthesis using MWH was approximately 7.9 kJ/mol, which is approximately one-tenth of the Q value (100.7 kJ/mol) for ZOFO using CH. It was determined that the inversion factors were approximately 5.4, 4.3, and 4.0, and the crystallite sizes
were 57.7, 72.5, and 78.9 nm for the ZAHFOH, ZNHFNH, and ZOFO, respectively. The ZFO powders exhibited superparamagnetism for ZAHFOH and paramagnetism for ZNHFNH and ZOFO. Based on the crystallite size-related surface effects, redistribution of the Zn and Fe ions occurred. This phenomenon
is attributed to the magnetic transformation of ZFO. Based on these results, it is expected that a sensitively tunable size and magnetic properties can be achieved using MWH.
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