Distinct nanostructures in (Co,Mn,Fe)3O4 were investigated using X-ray diffraction techniques combined with transmission and scanning transmission electron microscopy, as well as energy dispersive X-ray spectroscopy. The size of the checkerboard nanostructure increased with annealing, followed by the appearance of lamellar nanostructures comprising different types of platelike nanodomains because of nanoscopic spinodal decomposition of Mn and Fe ions. Remarkable local strain relaxation at the nanoscale associated with the domain size is suggested to play an important role in the stabilization of these checkerboard and lamellar nanostructures.
An infinite number of crystal structures in a multicomponent alloy with a specific atomic ratio can be devised, although only thermodynamically-stable phases can be formed. Here, we experimentally show the first example of a layer-structured pseudo-binary alloy, theoretically called Z3-FePd3. This Z3 structure is achieved by adding a small amount of In, which is immiscible with Fe but miscible with Pd and consists of an alternate L10 (CuAu-type)-PdFePd trilayer and Pd–In ordered alloy monolayer along the c axis. First-principles calculations strongly support that the specific inter-element miscibility of In atoms stabilizes the thermodynamically-unstable Z3-FePd3 phase without significantly changing the original density of states of the Z3-FePd3 phase. Our results demonstrate that the specific inter-element miscibility can switch stable structures and manipulate the material nature with a slight composition change.
This paper proposes a method that provides a phase image related to the demagnetization field (Hd) within a thin-foil permanent magnet using electron holography. The observation of Hd remains a significant challenge because electron holography in principle allows only imaging of the magnetic flux density (B), which is a mixture of the contributions from magnetization (M), stray magnetic field (Hs) outside of the specimen, and Hd inside of the specimen. The phase map approximating Hd, which was determined by processing of the electron holography observation from a Nd2Fe14B single-crystalline specimen, showed a good agreement with the prediction by micromagnetic theory. With respect to permanent magnets, this method can be applied to examinations about the coercivity mechanism which is sensitive to the demagnetization field.
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