摘要:

Transformations from ferrimagnetic to antiferromagnetic ordering with decreasing temperature have now been observed in manganese antimonides modified with V, Co, Cu, Zn, Ge, and As as well as with Cr. The magnetic structure change is accompanied by a first‐order change in the volume of the unit cell as well as a change in electrical resistivity. Crystallographic data for these materials in the exchange inversion region and at room temperature are presented as a function of the concentration of modifying element.

ISSN:0021-8979    

DOI:10.1063/1.1728723

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Various physical and chemical properties of the lanthanide hydrides suggest that they are saline in nature, the hydrogen existing as a negatively charged ion. These properties further suggest that the anionic charge is obtained from the conduction band of the lanthanide and that in the fully hydrogenated metal the conduction band is completely depopulated. Since coupling of the lanthanides occurs via the conduction electrons, this should lead to very considerable suppression of the interactions in the hydrides compared to the element, but an unchanged effective atomic moment. To determine whether this is the case susceptibility measurements have been made on a series of nine Ho&sngbnd;H alloys. These show for the dihydride, which still contains some conduction electrons, a Ne´el point at around 8°K (instead of 135°K for the element), whereas for the trihydride, which lacks conduction electrons, no Ne´el point is observed down to 4°K. Susceptibilities of the hydrides above about 15°K obey the Curie‐Weiss law with a much smaller Weiss constant than that for elemental holmium. The atomic moment is found, however, to be virtually unaffected by hydrogenation.

ISSN:0021-8979    

DOI:10.1063/1.1728724

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Relation of structure to magnetic susceptibility and internal friction is described for a 70% manganese‐30% copper alloy. The aged alloy exhibits a reversible fct to fcc transition at temperatures from 20° to 140°C, depending on the amount of aging. Magnetic susceptibility apparently obeys the Curie‐Weiss law but a change is observed in the temperature‐susceptibility curve at the structure transition temperature. The low‐stress internal friction of this alloy shows a resonance peak at the temperature of the structure change.Aging experiments with the 70 and 80% manganese alloys give evidence that quenching of alloys containing more than 80% manganese from solid‐solution temperatures does not prevent changes typical of alloys aged to initiate precipitation of alpha manganese. Thus the fct&rlarr2;fcc transformation that others have associated with the disappearance of antiferromagnetic ordering also is associated with an early stage of the alpha‐manganese precipitation.

ISSN:0021-8979    

DOI:10.1063/1.1728725

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Studies of EPR intensity and linewidth in four free radicals at temperatures between 300° and 1.5°K have shown the presence of antiferromagnetic exchange coupling. In two cases a low‐temperature paramagnetism occurs following a Curie‐Weiss law with positive Weiss constant. A model involving isolated spins in a magnetically dilute system is proposed to explain these results.

ISSN:0021-8979    

DOI:10.1063/1.1728726

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Magnetic susceptibilities of 14 iron‐vanadium alloys (to 26 at.% V) have been studied between their Curie temperatures and 1500°K. These alloys exhibit unusual paramagnetic behavior. Plots of the magnetic susceptibility vs vanadium concentration have a maximum which decreases with increasing temperatures. The curve of the paramagnetic Curie temperature vs at.% V also exhibits a maximum at about 10 at.% V. The paramagnetic moment per iron atom decreases gradually with the amount of vanadium in iron.

ISSN:0021-8979    

DOI:10.1063/1.1728727

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Metastable Co&sngbnd;Cu solid solutions in the concentration range between 12% and 95% Cu were obtained by simultaneous evaporation of Co and Cu on a cold substrate. The spin moment of the as‐deposited alloys is equal to that of Fe&sngbnd;Ni, Co&sngbnd;Ni, Ni&sngbnd;Cu solid solutions with the same average number of electrons per atom. During annealing at 700°C for a suitable time the spin moment increases to the value calculated for the two‐phase equilibrium state of the alloys. For an alloy with 65% Cu the Curie temperature is 580°K. All alloys have fcc structure before and after annealing.

ISSN:0021-8979    

DOI:10.1063/1.1728728

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Neutron diffraction has been performed on powder specimens of Mn2As and Mn2Sb0.7As0.3. Mn2As has the antiferromagnetic structure found in Mn1.9Cr0.1Sb below the exchange inversion temperature. The atomic moments are 3.7 and 3.5 Bohr magnetons for Mn(I) and Mn(II), respectively. The moments lie perpendicular to the tetragonal axis. The magnetic structure of Mn2Sb0.7As0.3, which undergoes exchange inversion over the 35° to 115°C temperature range, is the same as that of Mn2As at room temperature and is the same as that of ferrimagnetic Mn2Sb at 150°C. The atomic moments at room temperature (antiferromagnetic) are 2.3 and 2.8 Bohr magnetons, respectively, for Mn(I) and Mn(II). The moments are perpendicular to the tetragonal axis at room temperature and parallel to it at 150°C.

ISSN:0021-8979    

DOI:10.1063/1.1728729

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The imaginary part of the parallel pump susceptibility has been measured over a wide range of power levels and applied dc fields. Some of the structure present in the susceptibility curves is explained by a confluence process between two parametrically excited spin waves. The square of the frequency of the relaxation oscillations, which are frequently present in parallel pump excitation, has been found to increase linearly with the square of the magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.1728730

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Ferromagnetic resonance measurements have been performed on single‐crystal samples of the hexagonal ferrites BaFe12O19, Zn2Y, and Co2Y. Values of linewidth,gvalue, and anisotropy field are given as a function of temperature from 77°K to 600°K at various frequencies between 8 and 75 kMc. Zn2Y is singularly interesting because it exhibits an extremely narrow room temperature linewidth atXband. Values as low as 16 oe, with anisotropy fields of 9000 oe are reported. The theory of the resonance behavoir is developed and compared to the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.1728731

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Yttrium iron garnet has been crystallized on a seed crystal from molten BaO−xB2O3, wherexis 0.61. Two methods were used: (1) slow cooling of a melt in which a rapidly rotating seed was suspended, and (2) growth in a temperature gradient where excess yttrium iron garnet was maintained in a hotter part of the system, and a rapidly rotating seed was suspended in a cooler region. The geometry of the furnace, crucible, baffle, stirrer, and circulator system required to produce controlled growth in each of these systems is described, and the nature of the rate limiting step in each of the systems is discussed. The dependence of growth rate in the [110] direction on stirring rate, cooling rate, and solvent weight is presented. Good quality growth with rates as high as 50–75 mil/day was achieved in favorable cases.

ISSN:0021-8979    

DOI:10.1063/1.1728732

出版商:AIP    

年代:1962

数据来源: AIP