THE LOW-TEMPERATURE ORDERED STATE OF CERIUM MAGNESIUM NITRATE AND ITS INFLUENCE ON NUCLEAR ORIENTATION

1964 ◽  
Vol 42 (8) ◽  
pp. 1469-1480 ◽  
Author(s):  
J. M. Daniels ◽  
J. Felsteiner
Keyword(s):  
Magnetic Field ◽  
Nuclear Orientation ◽  
Dipole Interaction ◽  
Magnesium Nitrate ◽  
Divalent Ions ◽  
Antiferromagnetic Ordering ◽  
Γ Rays ◽  
Γ Ray ◽  
The Magnetic Field ◽  
Ordered State

The method of Luttinger and Tisza for minimizing the dipole–dipole interaction energy is applied to cerium magnesium nitrate, and an antiferromagnetic ordering of the cerium spins at 0 °K is found. Using this configuration, the magnetic field at the divalent ions is calculated. Next, the anisotropy of γ rays from Co60 aligned in this salt is calculated for temperatures below 0.003 °K. Qualitative agreement is found between these calculations and measurements of γ-ray anisotropy reported in the literature.

A COMPTON-ELECTRON γ-SPECTROMETER WITH TWO-DIRECTIONAL FOCUSING

1960 ◽  
Vol 38 (6) ◽  
pp. 720-750 ◽  
Author(s):  
G. E. Lee-Whiting
Keyword(s):  
Magnetic Field ◽  
Line Width ◽  
Cylindrical Symmetry ◽  
Maximum Efficiency ◽  
Electron Spectrometer ◽  
Γ Rays ◽  
Γ Ray ◽  
Compton Electron ◽  
Γ Spectrometer ◽  
The Magnetic Field

Improvements in the design of one type of Compton-electron spectrometer for γ-rays are proposed. The design requires a magnetic field of cylindrical symmetry and of slow radial variation, a simply curved radiator, and a system of apertures. Electrons are accepted only if they are ejected from the radiator with small components of momentum in two orthogonal directions perpendicular to the incident γ-ray. Since the magnetic field can also be used to measure the momentum of the selected electrons, the instrument can function as a γ-ray spectrometer. Higher-order aberrations are discussed, and a method of calculating the values of the various spectrometer parameters corresponding to maximum efficiency is given. Calculations of the intrinsic line-width, caused by the motion of the electron within the atom before collision with the photon, are carried out.

scholarly journals A lower limit to the magnetic field in the Crab Nebula from cosmic γ-ray experiments at 1011 eV

1970 ◽  
Vol 37 ◽  
pp. 250-256
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
G. H. Rieke ◽  
T. C. Weekes
Keyword(s):  
Magnetic Field ◽  
Lower Limit ◽  
Crab Nebula ◽  
High Energy ◽  
Secondary Products ◽  
High Energy Electrons ◽  
Γ Rays ◽  
Γ Ray ◽  
The Crab Nebula ◽  
The Magnetic Field

The 10-m optical reflector at Mt. Hopkins, Arizona, has been used to search for cosmic γ-Rays by the detection of atmospheric Čerenkov radiation from energetic particle showers. Approximately 100 drift scans of the Crab Nebula during 1968–69 have yielded no positive evidence of a γ-Ray flux. The upper limit to the flux at 1.7 × 1011 eV is 2.0 × 10−10 photons/cm2 sec. Assuming γ-Rays of this energy are produced by Compton scattering, a lower limit on the average magnetic field in the Crab Nebula is 1.5 × 10−4 gauss. This experiment also verifies previous evidence that the high-energy electrons in the Crab Nebula are not the secondary products of high-energy proton interactions but must have been accelerated from lower energies.

THE MEASUREMENT OF ENERGIES AND INTENSITIES OF γ-RAYS WITH A PAIR SPECTROMETER

1953 ◽  
Vol 31 (4) ◽  
pp. 537-576 ◽  
Author(s):  
B. B. Kinsey ◽  
G. A. Bartholomew
Keyword(s):  
Magnetic Field ◽  
Good Method ◽  
Counting Efficiency ◽  
Coincidence Spectrum ◽  
Slit Width ◽  
Experimental Point ◽  
Γ Rays ◽  
Γ Ray ◽  
The Magnetic Field ◽  
Good Agreement

The performance of a pair spectrometer of the Walker and McDaniel type is discussed from both a theoretical and an experimental point of view. It is shown that the energy of the γ-ray may be measured to a first approximation by the product of the distance between the inner edges of the slits which define the coincidence counters and the highest value of the magnetic field at which coincidences are found. A more accurate value of the energy of the γ-ray may be obtained by adding a small correction, called the "toe" correction, to the result so obtained. The magnitude of this correction is dependent on the γ-ray energy and on the width of the slits and is obtained from calculations of the shape of the coincidence peak based on the Bethe–Heitler formula. The correction depends very little on the length of the slits or on the thickness of the radiator. The relation between the calculated correction and the slit width has been examined experimentally. It is shown that the ultimate accuracy in energy measurement depends on the homogeneity of the magnetic field and on the error involved in the calculated toe correction. The latter error can be minimized by using very narrow slits and may be eliminated by plotting the value of magnetic field at the upper limit of the coincidence spectrum against the slit width and extrapolating the curve so obtained to zero slit width. The uncertainty in the magnetic field of the present instrument introduces a possible systematic error of about 0.05%. Measured values of the energies of a number of neutron capture γ-rays are compared with the values derived from the energy balance in (d, p) reactions. The results are in good agreement (within 0.1%).The relative counting efficiency as a function of energy is calculated theoretically and found to be in good agreement with experiment from 2.75 to 7.4 Mev. Above 7.4 Mev. no good method of checking the theoretical efficiency has been found. The absolute value of the counting efficiency at 2.75 and 7.38 Mev. has been measured by an ionization chamber method and is found to be in rough agreement with theoretical estimates.

Properties of HoV0 4 below 1 K III. A nuclear orientation study of the Van Vleck enhanced nuclear antiferromagnet holmium vanadate

1980 ◽  
Vol 372 (1748) ◽  
pp. 19-31 ◽  
Keyword(s):  
Nuclear Orientation ◽  
Dipole Interaction ◽  
Effective Field ◽  
Nuclear Magnetic Moment ◽  
Emission Anisotropy ◽  
Nuclear Moments ◽  
Adiabatic Demagnetization ◽  
Nuclear Orientation Study ◽  
Van Vleck ◽  
Ordered State

The y-ray emission anisotropy from the long-lived isomer 166m Ho ( I = 7) has been investigated in single crystals of the enhanced nuclear paramagnet HoVO 4 . From measurements in fields up to 2 T and temperatures between 45 and 65 mK, the nuclear magnetic moment of 166m Ho is determined as 3.60(5) pN. After adiabatic demagnetization, temperatures of approximately 1 mK were reached, and the nuclear ordered state has been studied. The results confirm that it is anti-ferromagnetic, and that the ordering is consistent with the predictions of Bleaney (1980), based on an effective field treatment of the dipole-dipole interaction between the enhanced nuclear moments. In particular, the spin-flop phase has been identified in fields of order 10 -2 T.

scholarly journals On the Predictive Power of the Minimum Energy Condition

1993 ◽  
Vol 157 ◽  
pp. 413-414
Author(s):  
Martin Pohl
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Predictive Power ◽  
Spiral Galaxies ◽  
Minimum Energy ◽  
Energy Condition ◽  
Cosmic Ray ◽  
Γ Ray ◽  
Minimum Energy Method ◽  
The Magnetic Field

We reexamine the minimum energy method to determine the magnetic field strength in spiral galaxies from the cosmic ray standpoint of view. It is shown that for example in M51 the estimated field strength is about a factor of 2 lower than obtained with the standard method. As a by-product the corresponding γ-ray flux from the galaxies can be calculated, which will allow further improvement of the method provided reliable γ-ray spectra are at hand.

NUCLEAR ORIENTATION IN ANTIFERROMAGNETIC SINGLE CRYSTALS

1961 ◽  
Vol 39 (1) ◽  
pp. 53-64 ◽  
Author(s):  
J. M. Daniels ◽  
J. C. Giles ◽  
M. A. R. LeBlanc
Keyword(s):  
Single Crystals ◽  
Nuclear Orientation ◽  
Γ Rays ◽  
Γ Ray

Mn54 and Co60 have been successfully oriented in five antiferromagnetic single crystals (MnCl2∙4H2O, MnBr2∙4H2O, CoCl2∙6H2O, Co(NH4)2(SO4)2∙ 6H2O, and MnSiF6∙6H2O) and the orientation was detected by the anisotropy of the emitted γ rays. Only in the case of Co60 in MnBr2∙4H2O was no γ-ray anisotropy seen. It is concluded that antiferromagnetism can be used as a means of producing nuclear orientation. Attempts to orient Br82 and 1131 in the manganese halides by superexchange were unsuccessful.

Magnetic Properties and Phase Diagram of Quasi-two-dimensional Na2Co2TeO6 Single Crystal Under High Magnetic Field

2021 ◽  
Author(s):  
Guiling Xiao ◽  
Zhengcai Xia ◽  
Yujie Song ◽  
Lixia Xiao
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Diagram ◽  
Magnetic Phase ◽  
Magnetic Coupling ◽  
Experimental Results ◽  
Antiferromagnetic Coupling ◽  
Magnetic Field Direction ◽  
Antiferromagnetic Ordering ◽  
The Magnetic Field

Abstract We investigated the magnetic characteristics of Na2Co2TeO6 at different temperatures and magnetic field. The experimental results indicated that the magnetic field can disturb the antiferromagnetic interaction and lead to the disorder. Magnetization curves measured with different angles θ (θ is between the magnetic field direction and c axis) express the magnetocrystalline anisotropy in this system. when the angle θ=0 (magnetic field parallel to c axis), two continuous magnetic phase transitions at critical temperature TN1 and TN3 were observed. As θ changes, TN1 is almost independent on θ, indicating the magnetic ordering at TN1 was a spontaneous behavior with a robust AFM characteristic. On the other hand, as θ increases from 0 to 180, TN3 presents extreme value at θ=90 (magnetic field perpendicular to c axis). It indicates that TN3 were sensitive to temperature and magnetic fields. At some angles closing to ab plane, an additional phase transition was observed at TN2. This phase transition at TN2 may mainly result from the long range antiferromagnetic ordering within ab-plane. Furthermore, the magnetization measurement up to 50 T revealed the strong antiferromagnetic coupling in the system, and in which the magnetic coupling within the honeycomb layers is strong and the magnetic coupling interaction between honeycomb layers is weaker. Based on the experimental results, we have obtained the complete magnetic phase diagram.

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