Magnetic order induced birefringence and critical behaviour of the long range order parameter in NiO

The optical linear magnetic birefringence of single-domain NiO crystals was measured at temperatures above and below the antiferromagnetic phase transition. The analysis of the experimental data yield a Néel temperature of T_N = (523.7 ± 0.2)K and a critical exponent β = 0.325^+0.01_-0.02 which determines the temperature behaviour of the magnetic long range order parameter $\text{S}\text{?}\text{～ (}\text{1?T}\text{T}{}_{\mathrm{N}}\text{)}{}^{\mathrm{\beta }}$. This critical behaviour of S? is found to be continued to temperatures well below T_N.     

Nuclear magnetic moment of the 3.9 s112− isomer 193mAu

The magnetic hyperfine splitting ν_M = |gμ_NB_HF/h| of ${}^{\mathrm{<mtext>193</mtext><mtext>m</mtext>}}\text{Au}\text{(j}{}^{\mathrm{\pi }}\text{=}\text{11}\text{2}{}^{\mathrm{?}}\text{, E = 290}\text{keV}$; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 3.9}\text{s}\text{)}$ as a dilute impurity in Ni has been measured with nuclear magnetic resonance on oriented nuclei as 226.4(2) MHz. With the known hyperfine field B_HF = ?264.4(3.9) kG corrected for hyperfine anomalies the g-factor and magnetic moment of ^193mAu are deduced to be |g| = 1.123(17) and |μ| = 6.18(9) μ_N.     

Nuclear magnetic moment of the 9.7 h 12− isomer 196mAu

The magnetic hyperfine splitting v_M=|gμ_NB_HF/h| of ^196mAu (j^π=12^?; configuration ¦(π$\text{11}\text{2}$($\text{v}\text{13}\text{2}{}^{\mathrm{+}}\text{)〉}{}_{12}{}^{\mathrm{?}}$; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 9.7}\text{h}\text{)}$ as dilute impurity in Ni has been determined with nuclear magnetic resonance on oriented nuclei as 96.0(2) MHz. With the known hyperfine field B_HF = ?264.4(3.9) kG corrected for hyperfine anomalies the g-factor and magnetic moment of ^196mAu are deduced to be |g| = 0.476(7) and |μ| = 5.72(8) μ_N. Taking into account the known magnetic properties of $\text{π}\text{1}\text{2}{}^{\mathrm{?}}$ and $\text{v}\text{13}\text{2}{}^{\mathrm{+}}$ isomeric states in the neighbouring odd Pt, Au and Hg nuclei the structure of the 12^? state is discussed.     

Magnetic field dependence of red emission intensity of ruby at various temperatures

Application of a magnetic field perpendicular to the c-axis of a thin slice of pink ruby at low temperatures reduces the intensity of R-line and vibronic emission. At field intensity H = 6 kG the loss of vibronic emission exceeds 10%. The decay time decreases by a similar fraction. The method used for studying intensity involves on-off modulation of the field, and digital integration. A function which describes the observed fractional reduction of intensity is $\text{F(H) =}\text{AH}{}^2\text{(1 + BH}{}^2\text{)}$ where A and B are nearly constant below 77 K, but decrease rapidly between 100 K and 200 K. The function can be derived by assuming that radiationless transitions to the ground state occur with probability proportional to H² from low-lying vibronic states of ²E. Thermal excitation from these states to states in the neighborhood of ²T₁ is proposed as the mechanism for quenching the magnetic field effects.     

Temperature variation of the magnetic cluster structures in an iron-nickel invar alloy

Small-angle scattering of long wavelength neutrons $\text{(λ = 6.42}\text{A}\text{?}\text{)}$ from an Fe₆₅Ni₃₅ single crystal has been measured with the applied magnetic field (6.2 kG) parallel and perpendicular to the scattering vector $\text{K}$ of the elastic scattering over the temperature range from 25 to 422°C (T_c = 227°C). The scattering cross sections due to the longitudinal spin fluctuation have been analyzed by means of Guinier's approximation $\text{(dσ/dω)}{}_0\text{exp}\text{(?κ}{}^2\text{R}{}_{\mathrm{<mtext>g</mtext>}}{}^2\text{3}\text{)}$, where the forward cross section (dσ/dω)₀ is proportional to n, which is the number of atoms in a paramagnetic cluster, and R_g is the radius of gyration of the cluster. The empirical relation between n and R_g is = 0.298 × R_g^2.34 to be compared with that calculated for a simple spherical cluster model n = 1.274 R_g³.     

Negative magnetoresistance in (SN)x single crystal

The magnetoresistance in (SN)x single crystals is composed of the normal positive and negative components. The former increases in proportion to the square of the magnetic field B². The latter is remarkable at temperatures below 4.2 K and saturates at relatively low magnetic field (? 30 kG). The coefficient $\text{S(=}\text{lim}\text{B→0}\text{{??}\text{(}\text{δρ}\text{ρ}{}_0\text{)}\text{?B}{}^2\text{})}$ of this negative magnetoresitance shows features similar to those of semiconductors with Toyozawa's theory. These results of negative magnetoresistance are explained in terms of carrier scattering by localized magnetic moments.     

g-factors of 2.7 h 93Tc, 4.9 h 94Tc and 20 h 95Tc

The hyperfine splitting frequencies gμ_NB_H.F./h of 2.7 h ⁹³Tc $\text{(J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$, 4.9 h ⁹⁴Tc (J^π = 7⁺) and 20 h ⁹⁵Tc $\text{(J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$ as dilute impurities in Fe have been measured with NMR on oriented nuclei as 336.36(5) MHz, 175.11(1) MHz and 315.97(2) MHz, respectively. From the resonance shifts with an external magnetic field B₀ the hyperfine field of Tc$\text{Fe}$ has been determined as -317(5) kG. Taking this into account the nuclear g-factors are deduced as $\text{g(}{}^{93}\text{Tc}\text{) = 1.392(22), g(}{}^{94}\text{Tc}\text{) = 0.725(11)}\text{and}\text{g(}{}^{95}\text{Tc}\text{) = 1.308(21)}$.     

A nucleon-nucleon potential that includes the effect of the N1(1236)

The transition potentials for the reaction $\text{N}\text{+}\text{N}\text{?}\text{N}\text{+}\text{N}{}^1\text{(1236)}$ and $\text{N}\text{+}\text{N}\text{?}\text{N}{}^1\text{(1236) +}\text{N}{}^1\text{(1236)+}\text{N}{}^1\text{(1236)}$ are derived in the case of the π and ? exchange using the quark model. The nucleon-nucleon scattering in the T=1, ¹S₀ state is treated as a coupled channel $\text{N}\text{+}\text{N}\text{?}\text{N}\text{+}\text{N}{}^1$ system.     

Phenomenological thermodynamics of mixed valence phenomenon

The fluctuation of valence in some rare-earth (RE) compounds is described in terms of the effective potential seen by the RE ion. The nearly degenerate $\text{4?}{}^{\mathrm{n+1}}\text{(5d6s)}{}^2$ and $\text{4?}{}^{\mathrm{n}}\text{(5d6s)}{}^3$ levels of the RE ion split in energy in the presence of a repulsive potential. The energy separation (ΔE) between these levels is a function of external variables such as temperature, pressure or composition, which change the effective potential seen by the ion. The variation of ΔE with temperature is obtained for four Europium compounds from ¹⁵¹Eu Mössbauer isomer shift data. The temperature dependence of susceptibility is then obtained from the same (ΔE) variation and compared with experimental results. A characteristic temperature (T_υ) is found below and above which (ΔE) behave as ΔE = αT and ΔE = βT+γ respectively.     

Measurement of the analyzing power of the 3He(d, p)4He reaction below 1 MeV

The analyzing powers iT₁₁, T₂₀, T₂₁ and T₂₂ have been measured for the reaction ³He(d, p)⁴He at laboratory energies of 344, 465 and 727 keV. A polarized deuteron beam was used with quantization axis oriented perpendicular to and at 54.7° to the incident beam direction. With semi-conductor proton detectors in two perpendicular planes all four analyzing powers could be determined. The beam polarization was determined using the ³H(d, n)⁴He reaction at a mean energy of 130 keV. The uncertainty in this analyzing power and the effect on the results is discussed. The analyzing powers have been fitted to a Legendre polynomial expansion to four or five terms and the resulting coefficients tabulated. The results indicate that d-waves contribute to the reaction only through the ${}^4\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ entrance channel and their contribution falls off both above and below the $\text{3}\text{2}{}^{\mathrm{+}}$ resonance at 430 keV.     

The effect of a non-minimally coupled scalar field upon classical thermodynamics

It is known that a scalar field that is non-minimally coupled to the geometry implies a varying gravitational “constant” G_eff, and hence a violation of the continuity equations, $\text{T}\text{?}{}^{\mathrm{ik}}{}_{\mathrm{;k}}\text{≠ 0}$, where $\text{T}\text{?}{}_{\mathrm{ij}}$ is the uncorrected energy-momentum tensor. This in turn upsets classical thermodynamics. 3he simplest resolution of this difficulty is to multiply all energetic quantities by $\text{G}{}_{\mathrm{<mtext>eff</mtext>}}\text{G}{}_{\mathrm{<mtext>N</mtext>}}$, where G_N is the newtonian gravitational constant. This modified thermodynamics is applied to the scalar-field version of the cosmological model of Zee, for which it is shown to cause restoration of the symmetry above some critical temperature T_c close to the Planck temperature. We also illustrate how the second law of thermodynamics is always obeyed, correcting a recent discussion by Davies.     

Simultaneous diffusion of calcium and strontium in KCl single crystals

Concentration dependent diffusion coefficients for ⁴⁵Ca²⁺ and ⁸⁵Sr²⁺ in purified KCl were measured using a sectioning method. KCl was purified by an ion exchange — Cl₂?HCl process and the crystals grown under $\text{1}\text{6}$ atmosphere of HCl. The tracers were purified on small disposable ion exchange columns to remove precessor and daughter impurities prior to use in a diffusion anneal. Isothermal diffusion anneals were made in the temperature range from 451% to 669%C. At temperatures above 580%C (the lowest melting eutectic in this system) diffusion was from a vapor source: below 580%C surface depositied sources were used. The saturation diffusion coefficients. enthalpies and entropies of impurity-vacancy associations were calculated using the common ion model for simultaneous diffusion of divalent ions in alkali halides. In KCl the saturation diffusion coefficients D_S(ca) and D_s(Sr) are given by

$\text{D}{}_{\mathrm{s}}\text{(Ca) = 9.93 × 10}{}^{\mathrm{?5}}\text{exp(?0.592}\text{eV}\text{kT}\text{)}\text{cm}{}^2\text{sec}$

(1) and

$\text{D}{}_{\mathrm{s}}\text{(Sr) = 1.20 × 10}{}^{\mathrm{?3}}\text{exp(?0.871}\text{eV}\text{kT}\text{)}\text{cm}{}^2\text{sec}$

(2) for calcium and strontium, respectively. The Gibbs free energy of association of the impurity vacancy complex in KCl for calcium can be represented by

$\text{Δg(Ca) = ?-0.507 eV + (2.25 × 10}{}^{\mathrm{?4}}\text{eV}\text{\%K}\text{)T}$

(3) and that for strontium by

$\text{Δg(Sr) = ?0.575 eV + (2.90 × 10}{}^{\mathrm{?4}}\text{eV}\text{\%K}\text{)T}$

. (4)     

Ni2+ emission in MgO,KMgF3, KZnF3 and MgF2

The emission of Ni²⁺ ions in MgO, KMgF₃, KZnF₃ and MgF₂ crystals has been investigated. The fine structure on the bands at about 20 000 cm^-1 and 13 000 cm^-1 has been studied in detail and from this and the excitation spectra these bands are assigned to ${}^1\text{T}{}_{\mathrm{2g}}\text{→}{}^3\text{A}{}_{\mathrm{2g}}$ and ${}^1\text{T}{}_{\mathrm{2g}}\text{→}{}^3\text{T}{}_{\mathrm{2g}}$ transitions respectively.     

N2+ bound quartet and sextet state potential energy curves

Potential energy curves for the ${}^4\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{u}}$, ${}^4\text{Π}{}_{\mathrm{g}}$ and ${}^6\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{g}}$ states of N⁺₂ that dissociate to N (${}^4\text{S}{}^0$) and $\text{N}{}^{\mathrm{+}}\text{(}{}^3\text{P)}$, have been determined from a complete active space self-consistent field calculation. The ${}^6\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{g}}$ state is found to be significantly bound (D_e = 2.68 eV) with a minimum at 1.72 Å.     

Magnetic moment of the 72+[404] ground state of 10.5 h 175Ta

The magnetic hyperfine splitting ν_M = |gμ_NB_HF/h| of ${}^{175}\text{Ta}\text{(J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}$; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 10.5}\text{h}\text{)}$ in Fe has been measured with the technique of nuclear magnetic resonance on oriented nuclei as 320.4(1) MHz. With the known hyperfine field $\text{B}{}_{\mathrm{<mtext>HF</mtext>}}\text{(}\text{Ta}\text{Fe}\text{) = ?648(13)}\text{kG}$ the magnetic moment of the $\text{7}\text{2}{}^{\mathrm{+}}\text{[404]}$ ground state of ¹⁷⁵Ta is deduced to be $\text{¦μ¦ = 2.27(5)μ}{}_{\mathrm{<mtext>N</mtext>}}$.     

Johnson noise and absolute temperature

Experimental evidence using Josephson junction devices has suggested that Johnson noise in copper fails to be proportional to absolute temperature below 10 millikelvin. A microscopic theory is presented which gives the Johnson noise temperature $\text{T}{}_{\mathrm{<mtext>J</mtext>}}\text{= ?}{}_0{}^1\text{XT}{}_0$ coth ($\text{XT}{}_0\text{T}$) dX where $\text{T}{}_0\text{=}\text{hν}{}_{\mathrm{<mtext>F</mtext>}}\text{2kN}$. For copper, the calculated T₀ = 3.84 mK agrees closely with the value extracted from experimental data, 3.89 mK. Within a few percent, $\text{T}{}_{\mathrm{<mtext>J</mtext>}}\text{? (}\text{T}{}_0\text{2}\text{)}$ coth ($\text{T}{}_0\text{2T}$), and this adequately fits the available experimental data. ν_F is the fermi velocity and N is the length of the resistor. The Johnson noise parameter “T₀” presumably can measure ν_F along different crystal orientations.     

The g-factor of the72+[404] ground state of 177Ta

With the technique of nuclear magnetic resonance on oriented nuclei the hyperfine splitting $\text{ν}{}_{\mathrm{<mtext>M</mtext>}}\text{= ¦gμ}{}_{\mathrm{<mtext>N</mtext>}}\text{B}{}_{\mathrm{<mtext>HF</mtext>}}\text{/h¦}\text{of}{}^{177}\text{Ta}\text{(j}{}^{\mathrm{\pi }}\text{7}\text{2}{}^{\mathrm{+}}\text{; T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 56.6h)}$ in Fe has been measured With the known hyperfine field $\text{B}{}_{\mathrm{<mtext>HF</mtext>}}\text{(}\text{Ta}\text{Fe}\text{) = ?648 (13)}\text{kG the}\text{g-}\text{factor of the}\text{7}\text{2}{}^{\mathrm{+}}\text{[404]}$ ground state of ¹⁷⁷Ta is deduced to be $\text{¦g¦ = 0.643 (13)}$.     

Magnetic phase transitions,anisotropic susceptibility and dipolar interactions in antiferromagnetic MnNb2O6

The magnetic properties of MnNb₂O₆ single crystals have been studied in the temperature range 1.6–300 K (T_N = 4.4 K), in fields up to 220 kOe. The high field saturation at low temperature, as well as the paramagnetic susceptibility at high temperature, agree well with a ${}^6\text{S}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ state for Mn²⁺ ions. From 1.6 to 3.8 K a spin flop is induced by fields ranging from 17 to 21 kOe, applied in the direction of the a-axis. Elements of the magnetic susceptibility tensors up to rank 12, measured below the spin flop field, are in accordance with a magnetic anisotropy originating mainly from magnetic dipolar interactions.