Pr Alloys Research Articles

On the nature of the dhcp to fcc transition under pressure in Pr and Pr-Th alloys

The results of electrical resistance (R), thermoelectric power (TEP) and X-ray diffraction measurements on praseodymium (Pr) and its alloys with thorium under pressure are reported. The maximum inR vsP curve exhibited by Pr persists only in the dhcp phase of PrTh alloy. X-ray measurements confirmed that in the alloys also the maximum inR vsP curve is due to the dhcp → fcc transition. Thus the behaviour of Pr and Pr-Th alloys is different from that of La and its alloys with Ce and Th where the maximum in theR vsP curve is electronic in origin and is exhibited by the dhcp, fcc and dist fcc phases.

Magnetic properties of amorphous Co-R ( R = Sm, Nd, Pr) alloys

Measurements of magnetization and susceptibility were carried out in the temperature range from 4.2 to 300 K for amorphous Co 100- x R x (R = Sm, Nd, Pr; 50 ⩽ x ⩽ 70) alloys prepared by a rapid quenching technique. The magnetic properties of these amorphous alloys are discussed based on a local moment model. It is concluded that the rare earth R in the amorphous alloys behaves as trivalent positive ions, and that the magnitude of effective magnetic moment inherent in Co ion decreases with an increase of x and almost vanishes around x = 60.

Magnetism of Rapidly Quenched Amorphous Fe-Sm Alloys

The structural analysis and investigation of magnetic properties were carried out on rapidly quenched Fe 100-x Sm x (10.5 ? × ? 80) alloys. Amorphous alloys were fabricated in a wide composition range from x = 17 to 72.5. The composition dependence of Curie temperature and magnetization was found to be similar to that of amorphous Fe-(Nd, Pr) alloys and could be considered to be caused by the change in short-range atomic order with Sm concentration. A maximum coercive force of about 1.1 kOe at 300 K and 12 kOe at 77 K is obtained in x = 40 alloy. The rapid decrease in coercive force on raising temperature can be explained by the wall pinning model proposed by Gaunt. After heating the amorphous alloys up to 900 K, they transform into metastable Fe 5 Sm (T c = 465 K) + ? - Fe (x ≪ 20), unknown metastable phase (T c = 555 K) + ? - Fe (20 ? × ? 33.3) and Fe 2 Sm (T c = 670 K) + Sm (x ? 40).

High pressure electrical resistance behaviour of Pr and Pr-Th alloys

High pressure electrical resistance behaviour of Pr and Pr-Th alloys

Magnetic properties of rapidly quenched amorphous Fe-Sm alloys

The structural analysis and investigation of magnetic properties were carried out on rapidly quenched Fe 100− x Sm x (10.5 ⩽ x ⩽ 80) alloys. Amorphous alloys are fabricated in a wide composition range from x = 17 to 72.5. After heating the amorphous alloys up to 900 K, they transform into metastable phase I ( T c = 465 K)+ α-Fe ( x < 20), metastable phase II ( T c = 555 K)+α-Fe (20 ⩽ x ⩽ 33.3) and Fe 2Sm+Sm ( x⩾40). The composition dependence of Curie temperature and magnetization is found to be similar to that of amorphous Fe-(Nd, Pr) alloys. A maximum coercive force of about 1.1 kOe at 300 K and 12 kOe at 77 K is obtained in the x = 40 alloy. The rapid decrease in coercive force with raising temperature can be explained by the wall pinning model proposed by Gaunt. The pronounced composition dependence of these magnetic properties for the amorphous Fe-Sm alloys can be considered to be caused by the change in the short-range atomic order with Sm concentration on the basis of the results of X-ray structural analysis.

溶湯急冷非晶質Ｆｅ‐Ｓｍ合金の磁性

The structural analysis and investigation of magnetic properties were carried out on rapidly quenched Fe100-xSmx (10.5≤x≤80) alloys. Amorphous alloys were fabricated in a wide composition range from x=17 to 72.5. The composition dependence of Curie temperature and magnetization was found to be similar to that of amorphous Fe-(Nd, Pr) alloys and could be considered to be caused by the change in short-range atomic order with Sm concentration. A maximum coercive force of about 1.1 kOe at 300 K and 12 kOe at 77 K is obtained in x=40 alloy. The rapid decrease in coercive force on raising temperature can be explained by the wall pinning model proposed by Gaunt. After heating the amorphous alloys up to 900 K, they transform into metastable Fe5Sm (Tc=465 K) + α-Fe (xTc=555 K) + α-Fe (20≤x≤33.3) and Fe2Sm (Tc=670 K) +Sm (x≥40).

Crystal field splittings in dilute amorphous rare earth alloys

Inelastic neutron scattering has been used in an attempt to characterize the crystal field of isolated rare earth ions in an amorphous matrix. Amorphous yttrium copper alloys in which 5% of the yttrium was replaced by Ce, Pr, and Er were studied using neutron time-of-flight spectroscopy. Both the Ce and Pr alloys showed quasielastic paramagnetic scattering at all temperatures between 15 and 300 K. The Er alloy however displayed a well defined inelastic peak centered at 2 meV at low temperatures which was identified with a crystal field transition. To our knowledge this is the first observation of a well-defined spectroscopic transition for rare earths in an amorphous environment.

Constitution, structure and magnetic properties of some rare-earth-cobaltaluminium alloys

The constitution and structure of the alloys represented by the formulae Ce1−x AlxCo5 and Pr1−xAlxCo5 (where 0⩽x⩽0.6) have been studied by X-ray diffraction and metallographic techniques. The substitution of between 1 and 3 at % Al (0.06⩽x⩽0.18) for Ce in CeCo5 produces a mixture of the 1∶5 and 2∶17 phases based on CeCo5 and Ce2Co17; there are two variations of the 2∶17 phase which are isostructural with the hexagonal Th2Ni17-type and rhombohedral Th2Zn17-type phases. At the composition Ce0.76Al0.24Co5 (4 at% Al) the alloy consists only of the 2∶17-type phases and metallographically the alloy is one phase in appearance. Further substitution of Al results in the precipitation of an fcc phase, based on the Co-Al solid solution, in the 2∶17 matrix. The crystal structures of the Pr1−xAlxCo5 alloys are very similar to those of the equivalent cerium alloys, although the ternary 2∶17-type phase has only the rhombohedral structure, as does the binary Pr2Co17 phase. The metallographic structures of the Pr alloys in the composition range 1 to 3 at% Al show significant differences from the corresponding Ce alloys. Determination of the Curie temperatures of theR1}-xAlxCo5 alloys (R= Ce and Pr) in the composition range 0⩽x⩽0.24 showed good agreement between the measured and published values for both the CeCo5 and PrCo5 phases. The Curie temperatures of the ternary 2∶17-type phases were approximately 50 K and 70 K lower than those of the binary, Ce2Co17 and Pr2Co17 alloys, respectively.

Magnetic and superconducting properties of dilute alloys of Pr in amorphous La 4Au

We report on magnetic and superconducting properties measurements on dilute alloys of Pr in amorphous La 4Au. Our results are compared with those obtained for Nd diluted in the same host. Low temperature departures from the Curie-Weiss law are attributed to “crystal field” effects. The abnormal concentration dependence of T c in Pr alloys might be due to a singlet ground state.

Observation of crystal field structure in the conductance of AlAl oxideBi1−xPrx tunnel junctions

Abstract Structure in the conductance of AlAl oxideBi1−xPrx tunnel juctions is compared with the theory of Holzer et al. predicting such structure due to scattering between crystal field split energy levels of the Pr impurity. The experimental results for x = 0.003 and 0.07 are shown to be in excellent agreement with the predictions of Holzer et al., if the crystal field split energy levels of Pr in these BiPr alloys are the same as those measured for bulk BiPr. The structure observed for x = 0.3, while being larger and more complicated than for the more dilute samples, is also shown to be explainable in terms of a modified crystal field split energy level scheme.

Resistivity of lanthanum, praseodymium and praseodymium-terbium alloys in d-hex phase

The influence of the crystal field on the electrical resistivity of Pr and the magnetically non dilute Pr-Tb alloys in the d-hex phase is analysed. The variation of the resistivity with the temperature is calculated using an expression derived by Maranzana and Bianchessi (1971) to the first order of the perturbation theory. The result of two sets of crystal field levels considered are discussed. The resistivity of La is discussed as phonon contribution to Pr and Pr-Tb alloys in d-hex phase.

High-Field Magnetization of Light Rare-Earth Metals

The magnetization of single crystals of Eu, Sm, Nd, Pr, and Pr-Nd alloys has been measured in fields up to 37 T (370 kG). The results give new information on the magnetic properties of these metals. Of particular interest is a first-order transition from a nonmagnetic to a metamagnetic phase in double-hexagonal close-packed Pr, due to the crossing of crystal-field levels, when a field of about 32 T is applied in the hard direction at low temperatures.

On the magnetic characteristics of Pr-La and Pr-Y alloys and the nature of elemental praseodymium at low temperatures

Magnetic susceptibilities of Pr and Pr-Y alloys are reported for the temperature range 2–300°K and for field strengths ( H) up to 21 kOe. The alloys show deviations from Curie-Weiss behavior and a tendency toward temperature-independent susceptibility similar to that exhibited by elemental Pr. χ at 4.2°K for Pr decreases sharply with alloying; its Weiss constant changes sign with as little as 10 per cent La or Y. χ at 4.2°K is observed to decrease with increasing H above 10 kOe; the decrease is progressively eliminated by alloying with Y or La, and also is not observed at 300°K. The operator equivalent method is used to calculate the energy level structure and associated magnetic moments for cubic and hexagonal Pr +3 ions. Influence of the sixth order term and H is included. Using standard formulae it is possible to account for the χ vs. T behavior for Pr 0.5La 0.5; the overall splittings at the cubic and hexagonal sites are the same as those found by Bleaney for Pr. Extension of the analysis to Pr enables most of its unusual characteristics to be understood. Appearance of spontaneous magnetization is predicted at T c , where T c is calculated to be in the range 24.4 to 32°K, depending on the choice of the molecular field coefficient. This compares favorably with 25°K observed by neutron diffraction techniques. From the analysis it is also clear why (a) the magnetic ordering in Pr is only a weakly cooperative process and (b) order is confined to the hexagonal sites. the new concept of Pr represents a way of harmonizing the two seemingly contradictory models used earlier in describing its low temperature magnetic behavior.