Date

October 1976

Document Type

Thesis

Degree Name

Ph.D.

Department

Dept. of Applied Physics

Institution

Oregon Graduate Center

Abstract

Various R[subscript x] (T,E)[subscript y] and (R,E)[subscript x] T[subscript y] alloys are studied, where R is Yttrium or a rare earth element, T is a 3d transition metal and E is an element to be substituted for either R or T. These alloys were studied with respect to structural stability, magnetic hardness and saturation magnetization. In the case of Sm [subscript.105] Fe [subscript.895-x] Al [subscript x] with x = 0.0 to 0.5, the Curie temperature (Tc) versus composition was investigated. The ternary compound Sm [subscript .167] Co [subscript.683] E [subscript .15] showed highly energetic domain walls of atomic dimensions when E is Si. The coercive field in this material (HC) at 4.2°K is 30 kOe for bulk materials and 28.5 kOe for powdered materials. The substitution of Ni or Cu for Co in SmCo [subscript 5] yielded relatively high values for HC while substitution of Ag or In [sic Indium] produced low values of HC. E = Pt or Au failed to stabilize the CaCu [subscript 5] structure. Replacing Sm in the lattice of R [subscript .167] Co [subscript.633] Al [subscript .20] by Ce and Tb produced low values of HC. Partial replacement of Sm by Zr according to Sm [subscript .167_x] Zr [subscript x] Co [subscript .833] to x = .134 showed both a decrease in HC and the anisotropy field (Ha). Within the Dy-Fe-Al ternary system, Dy [subscript .25]Fe[subscript.75-x]Al[subscript x] to x = .30, Dy.[subscript 207]Fe[subscript .793-x]Al[subscript x] to x = .20 and Dy[subscript .105]Fe[subscript .895-x]Al[subscript x] to x = .4475 were studied. A Curie type low dependence of HC versus temperature was observed in the Dy [subscript .25] Fe [subscript .75-x] Al [subscript x] compounds. At high Al substitution for T in these materials increasingly energetic, thin domain walls were observed from the 1:3 to the 2:17 alloys. The highest HC was found in Dy [subscript .105] Fe [subscript .4475] Al [subscript .4475]. Through extrapolation this field was estimated to be ~ 60 kOe. The pseudobinary Dy [subscript .25] Fe [subscript .75-x] Al [subscript x] indicated a phase transformation at x = .15 from the PuNi [subscript 3] isotype to the CeNi [subscript 3] structural type. The Th[subscript 2]Ni[subscript 17] structural type showed a narrow region of stability in the Dy[subscript .105]Fe[subscript .895-x]Al[subscript x] pseudobinary with the Th [subscript 2]Zn[subscript 17] isotype stable on both sides of this region. The two pseudobinaries, Sm[subscript .105]Fe[subscript .895-x]Al[subscript x] to x = .5 and Sm[subscript .105-x]Zr[subscript x]Co[subscript .895] to x = .04 were also studied. These both stabilized the Th [subscript 2] Zn [subscript 17] type structure. As in the case of SmCo [subscript 5] with Sm replaced by Zr, the 2:17 alloys exhibited disappointingly low values of HC. The Sm [subscript .105] Fe [subscript .895-x] Al [subscript x] alloys, on the other hand, showed a tendency towards moderately energetic domain walls, and an HC = 15 kOe in both the bulk and powdered materials was observed. Investigation revealed an initial increase in Tc up to 20 atomic percent of Al in Sm [subscript .105] Fe [subscript .895-x] Al [subscript x] with a subsequent decrease in Tc upon further Al substitution. The structural stabilities of the compounds investigated were considered on the basis of geometrical and deformable sphere packing factors. The nearest neighbor diagram is developed with respect to these factors. The role of the Ruderman, Kittel, Kasuya and Yosida (RKKY) exchange interaction in describing the magnetic properties of these alloys is also considered.

Identifier

doi:10.6083/M45H7D6V

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