Magnetic Behavior Of Mn Research Articles

Crystal field, electronegativity and magnetic behavior of Mn-, Fe-, Co- and Ni-doped LiMgN half-Heusler: KKR-CPA approximation

This paper aims to investigate the behavior of LiMgN half-Heusler (HH) semiconductor doped by transition metals (TM [Formula: see text] Mn, Fe, Co and Ni). HHs belong to the [Formula: see text] space group (No. 216) and have a zinc blende structure that can be described by the chemical symbol XYZ. The research methodology utilized in this investigation involves theoretical analysis based on the principles of density functional theory (DFT). The studied LiMg[Formula: see text]TM[Formula: see text]N alloy displayed the half-metallicity behavior when TM [Formula: see text] Fe, Co and Ni. Hence, these systems could be a promising candidate in spintronic application thanks to their ferromagnetism. The principal contribution to magnetism in the full LiMg[Formula: see text]TM[Formula: see text]N alloys comes from the Mn, Fe, Co and Ni doping. The partial magnetic moments of these elements are significantly greater than the combined partial magnetic moments of Li, Mg and N. When comparing LiMg[Formula: see text]Mn[Formula: see text]N to LiMg[Formula: see text]Fe[Formula: see text]N, 5Co[Formula: see text]N and LiMg[Formula: see text]Ni[Formula: see text]N, it is important to note that the exchange splitting energy [Formula: see text] associated to their spin up and spin down were discussed. The variation of Mn(3d) in relation to ([Formula: see text]) is larger than that of Fe, Co and Ni. Therefore, [Formula: see text]. Furthermore, there is a correlation between the magnetic moment and electronegativity trend of the TM dopant. Specially, the electronegativity trend ([Formula: see text] is well matched with the total spin moment trend, where [Formula: see text].

Structure, thermal stability and magnetic behavior of Mn(II) complexes with phenoxyacetic acid herbicides

The reaction of manganese(II) chloride with ammonium salt of 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-bromophenoxyacetic acid (4-Br) gave rise to the formation of hydrated complexes with formulas: Mn(MCPA)2·2H2O, Mn(2,4-D)2·2H2O and Mn(4-Br)2·3H2O. The compounds were characterized by elemental and thermal analyses, spectroscopic methods, as well as, by magnetic measurements. The complexes crystallize in monoclinic system. The Mn(II) ion is surrounded by oxygen atoms (from carboxylate groups and water molecules) in the octahedral arrangement. Variable-temperature (1.8–300 K) magnetic susceptibility measurements showed that compounds obey the Curie-Weiss law and have the paramagnetic properties. Being heated up to 1173 K the complexes decompose in three steps - first to anhydrous compounds: Mn(MCPA)2/Mn(2,4-D)2/Mn(4-Br)2 through intermediate products: MnO/Mn2OCl2/Mn2OBr2 to the following oxides: Mn2O3/Mn3O4/Mn3O4. The X-ray single crystal structure analysis was performed for Mn(II) complex with 4-bromophenoxyacetic acid after its recrystallization from N,N-dimethylformamide. The formation of hexanuclear cluster of manganese(II) carboxylate with a hydrophobic exterior was observed.

Ab initio study of magnetic properties of bimetallic Co n−1Mn and Co n−1V clusters

Spin-polarized density functional theory calculations on bimetallic Co n− 1Mn and Co n− 1V ( n = 2–9) clusters are reported. The clusters exhibit high stability at n = 6. With the exception of CoV, the magnetic moments of Co n , Co n− 1Mn and Co n− 1V increase with size by 3 μ B for n = 2–5 and by 1 μ B afterwards. The magnetic enhancement (reduction) is identified upon Mn (V) substitution, compared to Co n , consistent with recent experimental observation in large-sized clusters. Their different magnetic behavior of Mn and V-substituted clusters results from both differences in magnetic alignment (ferromagnetic in Co n− 1Mn and ferrimagnetic in Co n− 1V) and reduced local moments on Co in Co n− 1V.

Syntheses and magnetic properties of Cu(ii)(hfac)2and Mn(ii)(hfac)2complexes of 4-pyridyl-substituted thioaminyl radicals

Two types of Cu(II)(hfac)2 and Mn(II)(hfac)2 complexes of N-(4-pyridylthio)-4-ethoxycarbonyl-2,6-bis(4-chlorophenyl)phenylaminyl (1) and N-(4-pyridylthio)-2,4,6-tris(4-chlorophenyl)phenylaminyl (2) were prepared and their X-ray crystallographic and magnetic studies were performed. Mixtures of Cu(II)(hfac)2 and 1 and Mn(II)(hfac)2 and 2 in anhydrous heptane-benzene solution gave 1 : 2 complexes of M(II)(hfac)2 (M = Cu, Mn) and 1 or 2 in 73-75% yields. For Cu(II)(hfac)2(1)2 and Mn(II)(hfac)2(2)2 X-ray crystallographic analyses were successfully performed. The magnetic behaviors for the two metal complexes were investigated with a SQUID magnetometer. The analyses for the chimolTvs. T plots of Cu(II)(hfac)2(1)2 were carried out by the numerical diagonalization of the Heisenberg Hamiltonian matrix (4096 x 4096 matrix) for the four repeating units of the complex (12-spin system). The exchange interaction between the copper(II) ion and the thioaminyl radicals is ferromagnetic (J1/kB = +28 K) and the interactions between the complexes is antiferromagnetic (J2/kB = -13 K). The magnetic behavior of Mn(II)(hfac)2(2)2 complexes is well analyzed with the theoretical equation of a 1/2-5/2-1/2 three-spin system taking the intermolecular interaction (theta) into account. The exchange interaction between the Mn(II) ion and the thioaminyl radicals is antiferromagnetic (J/kB = -4.2 K) and theta = -1.0 K. These magnetic behaviors could be well explained in terms of their crystal structures.

Structure, bonding, and magnetism in manganese clusters

We investigate the structures and magnetic properties of small Mn(n) clusters in the size range of 2-13 atoms using first-principles density functional theory. We arrive at the lowest energy structures for clusters in this size range by simultaneously optimizing the cluster geometries, total spins, and relative orientations of individual atomic moments. The results for the net magnetic moments for the optimal clusters are in good agreement with experiment. The magnetic behavior of Mn(n) clusters in the size range studied in this work ranges from ferromagnetic ordering (large net cluster moment) for the smallest (n=2, 3, and 4) clusters to a near degeneracy between ferromagnetic and antiferromagnetic solutions in the vicinity of n=5 and 6 to a clear preference for antiferromagnetic (small net cluster moment) ordering at n=7 and beyond. We study the details of this evolution and present a picture in which bonding in these clusters predominantly occurs due to a transfer of electrons from antibonding 4s levels to minority 3d levels.

Magnetic Behavior of Mn3GaC under High Magnetic Field and High Pressure

We have measured the magnetization and magnetostriction of Mn 3 GaC in pulsed high magnetic fields up to 37 T and the magnetization under steady magnetic field and pressure up to 0.82 GPa. Mn 3 GaC is antiferromagnetic (AF) at low temperatures. It exhibits successive transitions to an intermediate (I), to a ferromagnetic (F) and to a paramagnetic phase. The transition between the AF and I phases is first order and the others are second order. The transition temperature between the I and F phases does not change greatly with increasing magnetic field. At low temperatures, a metamagnetic transition from the AF to the I state is observed. Volume magnetostriction measurement at 4.2 K indicates that the volume is abruptly decreased by the metamagnetic transition and then gradually shrinks with increasing field. High pressure stabilizes the F phase and enhances the Mn moment.

Magnetic and structural properties of Mn(SCN)2(CH3OH)2: A quasi-two-dimensional Heisenberg antiferromagnet.

The magnetic behavior of Mn(SCN${)}_{2}$(${\mathrm{CH}}_{3}$OH${)}_{2}$ in single-crystal form has been studied, and the crystal structure has also been determined. The system is monoclinic, C2/c, Z=4 with a=14.467(5) \AA{}, b=5.927(2) \AA{}, c=10.979(3) \AA{}, and \ensuremath{\beta}=93.19(3)\ifmmode^\circ\else\textdegree\fi{}. Manganese ions, of distorted octahedral coordination, are coupled together into quasi-two-dimensional arrays by bridging thiocyanate groups, and also by some hydrogen bonding. Potential interlayer-superexchange pathways are substantially less efficient, though probably not insignificant either. The magnetic properties seem consistent with the structural features. The single-crystal susceptibility exhibits uniaxial anisotropy in the paramagnetic regime, with ${\mathrm{\ensuremath{\chi}}}_{\mathit{a}}^{\mathrm{*}}$ somewhat larger than ${\mathrm{\ensuremath{\chi}}}_{\mathit{b}}$\ensuremath{\approxeq}${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$. A broad maximum appears at 12.6(4) K in ${\mathrm{\ensuremath{\chi}}}_{\mathit{b}}$ and ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$, and a sharper maximum at 10.5 K in ${\mathrm{\ensuremath{\chi}}}_{\mathit{a}}^{\mathrm{*}}$.An antiferromagnetic transition at 10.5(2) K is also apparent in the b- and c-axis susceptibilities, and below this temperature substantial anisotropies appear. A weak ferromagnetic moment develops along the b axis below 10.5 K, and from the magnitude of the spontaneous moment along this axis it is deduced that the spins are canted 0.20\ifmmode^\circ\else\textdegree\fi{} from the c axis toward b. A possible spin-reorientation transition at 3.${7}_{5}$ K is also apparent. High-temperature series-expansion fits to the susceptibilities suggest that a two-dimensional Heisenberg model is appropriate, but that interlayer exchange cannot be neglected; derived parameters are J/k=-0.70(3) K and J'/k=-0.16(2) K. The anisotropy observed in the paramagnetic regime suggests that a rather strong single-ion anisotropy of the form D[S^ $_{\mathit{z}}^{2}\mathit{S}$(S+1)/3], with D/k=0.29(2) K, is also present. The results are compared with various theoretical predictions for two-dimensional and three-dimensional models, and it appears that the system is more or less intermediate between these two lattice dimensionalities. The canting that is observed is almost certainly due to site-inequivalent single-ion anisotropy rather than to antisymmetric exchange. A detailed consideration of intralayer- and interlayer-superexchange pathways is also presented, and rather satisfactorily accounts for the observed differences in exchange interactions between this system and the analogous ethanol compound.

Magnetic behavior of Mn 1- tCr tas under pressure

The magnetic properties of Mn 1- t Cr t As (0.1 < t ⩽ 1.0) under hydrostatic pressure up to 10 kbar and quasi-hydrostatic pressure up to 30 kbar at temperatures 4.2–370 K have been studied by magnetization and resistivity measurements. It is found that under pressure in the range 0.1 < t < 0.9 magnetic phases of ferromagnetic type appear. At 0.1 < t 0.4 the situation is analogous to that observed earlier in orthorhombic MnAs and in Mn 1- t Fe tAs (0.03 < t < 0.1). In Cr rich samples the spontaneous magnetization appearance can be attributed to a conical deformation of the double spiral magnetic structure H c . The origin of this deformation is discussed.

Magnetic behavior of Mn(NH4)2(SO4)2 � 6H2O in its Curie region in fields directed along theb-axis

The intensity of magnetization and the isentropic magnetic susceptibility of Mn(NH4)2(SO4)2 · 6H2O have been determined along 13 isentropes (between 0.620 and 2.825 cal mole−1 deg−1) in fields up to 1670 Oe directed along theb-axis of a spherical single crystal. Eleven of the isentropes originated, in zero field, within the Curie region of the salt. Field increments of 10 to 15 Oe were used below 170 Oe, with larger steps above this. All isentropes originating within the Curie region show a common (high) susceptibility at zero field. In each case the susceptibility then drops sharply at a small field characteristic of the particular entropy. The drop in susceptibility was used to define the boundaries of the Curie region (critical fieldvs entropy). The change of temperature with magnetic field was determined along the isentropes and examples are given.