Spin-orientation diagram of the pseudobinaryTb1−xDyxFe

Abstract

Comments and AddendaThe section Comments and Addenda is for short communications which are not appropriate for regular articles. It includes only the following types of communications: (I) Comments on papers previousLy published in The Physical Review or Physical Review Letters.(2) Addenda to papers previously published in The Physical Review or Physical Review Letters, in which the additional information abstract for information-retrieval purposes. Accepted manuscripts folio~the same publication schedule as articles in this journal, and page proofs are sent to authors.The spin-orientation diagram of Tb, "Dy"Fe2 is constructed by Fe Mossbauer measurements and compared with single-ion calculations. The 4f-crystal-field interaction dominates the magnetocrystalline anisotropy properties, though the presence of additional contributions to the magnetic anisotropy free energy is indicated.Nonmajor cubic symmetry axes of easy magnetization have been established in some mixed rareearth ternary R', , R', Fe~, " as well as in binary CeFe"' SmFe"' and HoFe, ' cubic Laves cornpounds. These unusual axes of magnetization were found to occur over a relatively broad temperature interval, within which the easy axis of magnetization n rotates continuously over a wide range of directions, usually from one major cubic axis to another. It was believed" that the appearance of unusual, or transition regions, in the spinorientation diagrams of the R, ,R, Fe, compounds, is due either to coexisting domains of different major-axis spin alignments, or to additional, noncubic anisotropies, besides that which arises from the 4f-crystal-field interaction. Recent calculations' have demonstrated that the single-ion model, applied to the rare-earth ion, accounts for unusual axes of easy magnetization within the framework of cubic symmetry. These calculations involved the diagonalization of the single-ion Hamiltonianwith the 4f-crystal-field interaction the only source of magnetocrystalline anisotropyfor n parallel to the three major cubic axes, as well as for other directions of n which were confined to the (110) and (100) planes. Using the eigenvalues of the single-ion Hamiltonian, the magnetocrystalline anisotropy free energy per ion F"(n, T) is calculated. For a ternary R, "R"Fe,compound F(x, n, T) =(1x)Fsx(n, T) + xF"a(n, T) .The easy direction of magnetization, of a given composition, at a given temperature, is that for which the free energy has its lowest value.We report "Fe Mossbauer-effect measurements that were made in order to reexamine and supplement the previously reported' spin-orientation diagram of the Tb, , Dy"Fe, system. The analysis of the present Mossbauer results of Tb, "Dy"Fe, follows a least-squares-fitting procedure which is described elsewhere, " and enables determination of the direction of n relative to the cubic-cell axes. The present study was prompted by the single-ion calculations, ' which revealed regions of unusual spin alignments in Tb, "Dy, Fe"at temperatures and compositions that have not been investigated be...

Morphotropic Phase Boundaries in Ferromagnets:Tb1−xDyxFe2Alloys

“…Our measurements are summarized in the phase diagram of Fig. 1 and compared with previous measurements [11,12] plus the results of single ion crystal field theory. We find that the MPB region, across which phases coexist, widens with increasing temperature.…”

Local rhombohedral symmetry in Tb0.3Dy0.7Fe2 near the morphotropic phase boundary

“…Similar to ferroelectric MPBs, the already reported Tb 1Àx Dy x Co 2 6 and Tb 1Àx Dy x Fe 2 7 systems also show the flattened free energy landscape, which results in the coexistence of two low-symmetry phases and the significantly enhanced fieldinduced strain at MPB. Consequently, this offers a magnetostructural origin for the well-known Terfenol-D giant magnetostrictive materials (GMMs) with compositions near MPB (typically, Tb 0.3 Dy 0.7 Fe 2 ) , [9][10][11][12] which can generate high magnetostriction at low switching fields. MPB in Tb 1Àx Dy x Fe 2 was previously known as a "spin-orientation transition" that has been explained by single-ion theory, 10 but how maximum magnetostriction appears is unclear.…”

“…Previously, it has been long believed that this alloy keeps C15 MgCu 2 -type cubic Laves phase structure across each transition, which is known as the Curie transition and spin reorientation transition (SRT), respectively. 10 Recent precise electrical and thermal measurements have demonstrated that the Curie transition has first-order features, i.e., small thermal hysteresis and latent heat. 24 The structure for Tb 0.3 Dy 0.7 Fe 2 below Curie temperature T C is thus having lower crystal symmetry.…”

Магнитострикционные аномалии редкоземельных фаз Лавеса c морфотропным фазовым переходом

“…Редкоземельные фазы Лавеса RT 2 (R -редкоземельный элемент; T -3d-переходный металл) уже более полувека вызывают большой интерес специалистов в области как физики конденсированных сред, так и функциональных материалов, благодаря разнообразию наблюдаемых в них физических явлений, таких как гигантская магнитострикция, магнитокалорический и магнитоэлектрический эффекты [1][2][3][4][5][6][7][8][9][10]. Наиболее известной является система TbFe 2 −DyFe 2 , в которой при определенных условиях состава и температуры можно достичь компенсации магнитокристаллической анизотропии (МКА) и получить состав с гигантскими значениями магнитострикции (λs ∼ 2000 ppm) в слабых магнитных полях в широкой области температур.…”

“…Наиболее известной является система TbFe 2 −DyFe 2 , в которой при определенных условиях состава и температуры можно достичь компенсации магнитокристаллической анизотропии (МКА) и получить состав с гигантскими значениями магнитострикции (λs ∼ 2000 ppm) в слабых магнитных полях в широкой области температур. В области комнатной температуры таким составом является Tb 0.3 Dy 0.7 Fe 2 , известный как Терфенол-D [2,6]. Данный материал широко используется в высокочувствительных датчиках, источниках ультразвука и других механизмах [11][12][13].…”