Certain R2Co17 and R2 T14 B systems (R = a rare earth, T = Fe or Co) are of significance for use in the fabrication of high energy magnets. Improvements in these systems as high energy magnet materials are effected by partially replacing Co or T by appropriate d transition metals. A description is given of the magnetic behavior of a number of systems based on R2 Co17 and R2T14 B. Also, an account is given of recent work dealing with the systems RCo4 B and PrCo4-xFex B. The latter materials have large magnetizations and high Curie temperatures. However, they are not useful permanent magnet materials because they exhibit planar anisotropy. Results of some Auger spectroscopy studies of R2 Fe14 B systems (R = Pr,Nd or Er) are presented. This work shows the intergranular region to be rich in B, O and R. This region is undoubtedly non-magnetic, a feature which is most probably of significance in regard to the observed coercivity of R2 Fe14 B magnets.

A jökulhlaup burst from the head of Grasshopper Glacier in Wyoming's Wind River Mountains during early September 2003. Five reaches with distinct sedimentation patterns were delineated along the Dinwoody Creek drainage. This paper focuses on a portion of the jökulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters. Aggradation within the main channel upstream from each logjam created local sediment wedges, and the jams facilitated overbank deposition during the jökulhlaup. Field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features, as well as initial modification of the logjams and flood deposits within the normal seasonal high-flow channel. Overbank deposits have not been altered by flows occurring since 2003. Field measurements supported three hypotheses that (i) logjams present along the forested portions of the jökulhlaup route are larger and more closely spaced than those along adjacent, otherwise comparable stream channels that have not recently experienced a jökulhlaup; (ii) logjams are not randomly located along the jökulhlaup route, but instead reflect specific conditions of channel and valley geometry and flood hydraulics; and (iii) the presence of logjams facilitated significant erosional and depositional effects. This paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel, and thus the formation of large logjams. These logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges, and through this process promote valley-bottom aggradation and sediment storage. Changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley-bottom dynamics in these environments, which is particularly relevant given predictions of worldwide global warming and glacial retreat. Processes observed at this field site likely occur in other forested catchments with headwater glaciers.

Magnetic properties of R2Fe14 − xMnxB systems (R ≡ Y, Nd, Pr, Gd) were investigated over a large temperature range. All the compounds studied crystallized in the tetragonal R2Fe14B structure. The substitution of iron by manganese rapidly decreased the Curie temperatures and saturation moments. The anisotropy field HA at 77 K is found to increase, especially for R ≡ Pr compounds. The spin-reorientation temperature is lowered by manganese substitution for the Nd2(Fe, Mn)14B systems, and the cone angle θ is also reduced.

Effects of a small amount of Ti, Zr and Hf on the magnetocrystalline anisotropy of Cu-doped Pr2Co17 has been studied on the Pr2(Co16Cu1)(17-x)/17Mx system to obtain a better understanding of the magnetic hardness of the commercially av ailable “2:17-type” permanent magnets. All the compounds studied occurred in the rhombohedral structure. The c/a ratio was found to increase when M = Ti and decrease when M = Zr or Hf as the M atoms replace Co or Cu atoms. Distinct evidences of spin reorientation were observed in the M-doped compounds from magnetic and X-ray diffraction studies. The results are discussed in the terms of a switch of magnetocrystalline anisotropy of the Co sublattice from planar to uniaxial due to the M substitution.

R2(Fe, Co)14B compounds (R = Y, Nd and Gd) were prepared in high purity. The magnetic behavior of R2(Fe, Co)14B compounds is reported over the temperature range 4 to 300 K. The effects of Fe substitution by Co on the saturation magnetization, Curie temperature and anisotropy are presented. The spin-reorientation temperature is lowered as Co replaces Fe. This also results in a reduced cone angle.

Magnetic characteristics of Ti-, Zr- and Hf-substituted PrCo5 alloys have been studied over the temperature range from 77 to 300 K and for applied fields up to 20 kOe. It is established that Ti, Zr and Hf substitute for Pr. Single-phase materials are formed for all values of x up to 0.2 in the system Pr1−xZrxCo5 but for x only up to 0.1 for Pr1−xTix Co5 and Pr1−xHfxCo5 alloys. Larger amounts of Zr can be substituted if the material is made hyperstoichiometric in Co, e.g., Pr0.7Zr0.3Co5.5. All the alloys show a decrease in magnetic moment and an increase in Curie temperature as x increases. Anisotropy fields decrease as x increases at 295 K. Anomalous behavior is observed at 77 K, suggested that these ternary alloys may have a cone structure at this temperature.

R2Fe14B compounds, R = Pr, Nd, Dy, or Er, were prepared from high purity rare earths obtained from the Ames Laboratory. The magnetic properties of these and related systems with other rare earths are under investigation in our laboratories. In the present study magnetic susceptibilities were determined from the Curie temperature (TC) (556–596 K) up to a characteristic temperature Tt. Above Tt the susceptibility was observed to increase sharply and to become history-dependent, suggesting sample decomposition or a phase change. Tt = 830, 920, and 960 K for R = Pr, Nd, and Er, respectively. Curie–Weiss behavior is observed for the Pr and Nd compounds but not for Dy2Fe14B and Er2Fe14B. The susceptibility of the latter material follows the hyperbolic form described by Néel, i.e., 1/χ=1/χ0+T/C−σ/(T−θ). For R=Pr and Nd, near TC χ follows the expression χαt−γt=(T−TC)T−1C]. γ=1.37 for R=Pr and 1.41 for R = Nd. The iron paramagnetic moments are 4.02, 4.06, 4.09, and 4.10 μB for Pr2Fe14B and Nd2Fe14B, Dy2Fe14B and Er2Fe14B, respectively, which are close to the value (3.97 μB) obtained for Y2Fe17. The Weiss constants are 575 and 602 K, respectively, for Pr2Fe14B and Nd2Fe14B. Results indicate little itineracy of the 3d electrons in the R2Fe14B systems.

Commercially procured rare earth metals frequently contain 2–5 atomic per cent oxygen. Rare earth intermetallic compounds prepared from these materials with compositions estimated by synthesis can significantly deviate from the intended composition. Several R2Fe14B systems have been synthesized using rare earth metals obtained from the Ames Laboratory which typically contain <25 ppm oxygen (by weight) and their fun damental magnetic properties determined. Curie temperatures range from 565 (for Y2Fe14B) to 669 K (for Gd2Fe14B). Anisotropy fields (20 C) range from 27 to 71 kOe. Results for Y2Fe14B and Gd2Fe14B suggest that about 40% of the anisotropy in Nd2Fe14B originates with the Fe sublattice. The Fe moment in these systems exceeds by a small margin that of elemental Fe, suggesting that B is acting as an electron donor. The Nd moment in Nd2Fe14B is estimated as 3.0 μB, which is 92% of the free ion moment. The NdFe and GdFe couplings are ferromagnetic and antiferromagnetic, respectively. Coupling for these systems conforms to the systematics observed earlier for simpler rare earth intermetallics.

Chemischer InformationsdienstVolume 16, Issue 19 Reviews ChemInform Abstract: RECENT ADVANCES IN THE STUDY OF THE MAGNETISM OF LANTHANIDE INTERMETALLICS AND THEIR HYDRIDES W. E. WALLACE, W. E. WALLACESearch for more papers by this authorH. FUJII, H. FUJIISearch for more papers by this authorE. BOLTICH, E. BOLTICHSearch for more papers by this authorS. HIROSAWA, S. HIROSAWASearch for more papers by this authorF. POURARIAN, F. POURARIANSearch for more papers by this authorM. MERCHES, M. MERCHESSearch for more papers by this authorE. OSWALD, E. OSWALDSearch for more papers by this authorE. SCHWAB, E. SCHWABSearch for more papers by this authorM. V. SATYANARAYANA, M. V. SATYANARAYANASearch for more papers by this author W. E. WALLACE, W. E. WALLACESearch for more papers by this authorH. FUJII, H. FUJIISearch for more papers by this authorE. BOLTICH, E. BOLTICHSearch for more papers by this authorS. HIROSAWA, S. HIROSAWASearch for more papers by this authorF. POURARIAN, F. POURARIANSearch for more papers by this authorM. MERCHES, M. MERCHESSearch for more papers by this authorE. OSWALD, E. OSWALDSearch for more papers by this authorE. SCHWAB, E. SCHWABSearch for more papers by this authorM. V. SATYANARAYANA, M. V. SATYANARAYANASearch for more papers by this author First published: May 14, 1985 https://doi.org/10.1002/chin.198519348AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue19May 14, 1985 RelatedInformation

Commercial rare earth metals contain several atomic % oxygen, and intermetallics synthesized using these ingredients deviate markedly from the intended compositions. In this work, high purity rare earths (<20 ppm oxygen by weight) were used. Results for R2Fe14B systems with R = Y, Nd, Sm, or Gd have been previously reported. The earlier work has now been extended to include systems containing Ce, Pr, Dy and Er. All were ordered magnetically at room temperature, with Curie temperatures ranging from 437 K (Ce) to 592 K (Dy). Results suggest that Ce in this system exists in the quadripositive state. Saturation magnetizations (77 K) are 29.4, 34.8, 12.1, and 14.7 μB/formula unit, respectively, for R = Ce, Pr, Dy, and Er. These may be contrasted with 30.4 μB/f.u. for Y2Fe14B, which is the Fe magnetization alone. These results imply ferromagnetic coupling for Pr2Fe14B and antiferromagnetic coupling for the Dy and Er compounds. Room temperature anisotropy fields ranged from 37 kOe (R = Ce) to 158 kOe (R = Dy). Er2Fe14B exhibits a spin reorientation near room temperature. Pr2Fe14B, unlike Nd2Fe14B, exhibits no spin reorientation.

PrCo5permanent magnets have been produced with energy products ranging up to 26 MGOe and which are magnetically and chemically stable. These magnets typically have remanence of ∼ 10.5 kG and a coercive force of 4 to 5 kOe. The maximum energy product achieved is only about 60% of that theoretically possible, 39 MGOe. The low coercive force is ascribed to impurity phases Pr5Co19or Pr2Co17, which are formed in the sample as a result of oxidation or of imperfect compensation for the effects of oxidation.