Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPressure-Induced Enhancement of the Magnetic Anisotropy in Mn(N(CN)$_{2}$)$_{2}$
283
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Using dc and ac magnetometry, the pressure dependence of the magnetization of the three-dimensional antiferromagnetic coordination polymer Mn(N(CN)$_{2}$)$_{2}$ was studied up to 12 kbar and down to 8K. The magnetic transition temperature, $T_c$, increases dramatically with applied pressure $(P)$, where a change from $T_c(P=text{ambient}) = 16.0$ K to $T_c(P=12.1$~kbar$) = 23.5$ K was observed. In addition, a marked difference in the magnetic behavior is observed above and below 7.1 kbar. Specifically, for $P<7.1$ kbar, the differences between the field-cooled and zero-field-cooled (fc-zfc) magnetizations, the coercive field, and the remanent magnetization decrease with increasing pressure. However, for $P>7.1$ kbar, the behavior is inverted. Additionally, for $P>8.6$ kbar, minor hysteresis loops are observed. All of these effects are evidence of the increase of the superexchange interaction and the appearance of an enhanced exchange anisotropy with applied pressure.
rate research
Read More
We investigate the temperature dependence of the pressure-induced softening in the negative thermal expansion material Zn(CN)$_2$ using neutron powder diffraction and molecular dynamics simulations. Both the simulation and experiment show that the pressure-induced softening only occurs above a minimum temperature and also weakens at high temperatures.
We theoretically investigate the interplay between local lattice distortions around $rm{Mn^{2+}}$ ion impurity and the ions magnetic polarization, mediated through spin-orbit coupling of hole. We show that the tetrahedral symmetry around $rm{Mn^{2+}}$ ion impurity is spontaneously broken even in the paramagnetic regime. Modest local lattice distortions around the impurity $rm{Mn^{2+}}$ ion, along with the growth strain, stabilize magnetization along $< 110 >$ directions, in the ferromagnetic regime. We explain the experimentally observed in-plane uniaxial magnetic anisotropy seen in this system using this symmetry-breaking mechanism.
The dependence of the magnetic anisotropy of As-capped (Ga,Mn)As epilayers on the annealing parameters - temperature and time - has been investigated. A uniaxial magnetic anisotropy is evidenced, whose orientation with respect to the crystallographic axes changes upon annealing from [-110] for the as-grown samples to [110] for the annealed samples. Both cubic an uniaxial anisotropies are tightly linked to the concentration of charge carriers, the magnitude of which is controlled by the annealing process.
Here we report the synthesis of metallic, ultraincompressible (bulk modulus $K_{0}$ = 428(10) GPa) and very hard (nanoindentation hardness 36.7(8) GPa) rhenium (V) nitride pernitride Re$_{2}$(N$_{2}$)N$_{2}$. While the empirical chemical formula of the compound, ReN$_{2}$, is the same as for other known transition metals pernitrides, e.g. IrN$_{2}$, PtN$_{2}$, PdN$_{2}$ and OsN$_{2}$, its crystal chemistry is unique. The known pernitrides of transition metals consist of a metal in the oxidation state +IV and pernitride anions N$_{2}^{4-}$. ReN$_{2}$ contains both pernitride N$_{2}^{4-}$ and discrete N$^{3-}$ anions, which explains its exceptional properties. Moreover, in the original experimental synthesis of Re$_{2}$(N$_{2}$)N$_{2}$ performed in a laser-heated diamond anvil cell via a direct reaction between rhenium and nitrogen at pressures from 40 to 90 GPa we observed that the material was recoverable at ambient conditions. Consequently, we developed a route to scale up its synthesis through a reaction between rhenium and ammonium azide, NH$_{4}$N$_{3}$, in a large-volume press at 33 GPa. Our work resulted not only in a discovery of a novel material with unusual crystal chemistry and a set of properties attractive for potential applications, but also demonstrated a feasibility of surmounting conceptions common in material sciences.
Using first-principles calculations, we investigated the impact of chromium (Cr) and vanadium (V) impurities on the magnetic anisotropy and spin polarization in Fe/MgO magnetic tunnel junctions. It is demonstrated using layer resolved anisotropy calculation technique, that while the impurity near the interface has a drastic effect in decreasing the perpendicular magnetic anisotropy (PMA), its position within the bulk allows maintaining high surface PMA. Moreover, the effective magnetic anisotropy has a strong tendency to go from in-plane to out-of-plane character as a function of Cr and V concentration favoring out-of-plane magnetization direction for ~1.5 nm thick Fe layers at impurity concentrations above 20 %. At the same time, spin polarization is not affected and even enhanced in most situations favoring an increase of tunnel magnetoresistance (TMR) values.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
