Exchange interactions and magneto-crystalline anisotropy in RFe12−M and parent interstitial compounds

Influence of H and N insertion on the magnetostriction and thermal expansion of YFe10V2Zx (Z=N, H) compositions

“…H, N and C), so that some of them (particularly, NdFe 10.5 V 1.5 ) exhibit intrinsic ferromagnetic properties better than those of Nd 2 Fe 14 B, the archetype of permanent magnet materials. In this respect, much attention has been paid on the effect of interstitial atoms on the crystallographic structure and magnetic properties of these compounds [1][2][3][4][5][6][7][8][9][10][11][12][13]. The purpose of this research is to study the influence of H and N interstitial atoms on the magnetoelastic properties of YFe 10 V 2 compound, which have been rather less considered until now.…”

“…From a different viewpoint, the second-order crystal field parameter (A o 2 ), and accordingly the magnetic anisotropy, is oppositely influenced by donor and acceptor interstitial elements. For example, insertion of the H + (N À ) enforces the negative (positive) contributions to A o 2 [4,5], so that the planar (axial) magnetic anisotropy is strengthened in the REFe 12Ày M y compounds whenever RE is a rare earth element with negative Stevens factor (i.e. a j o0), such as Nd.…”

Magnetostriction and thermal expansion of interstitially modified NdFe10V2Zx (Z=N, H) compounds

“…Otherwise for temperatures below the spin reorientation temperature T SR = 130 K, the thermal expansion coefficient of the interstitially modified compounds are larger than that of the host compound. These observations can be described as due to the effect of interstitial atoms on the magnetic anisotropy of NdFe 10 V 2 compound for temperatures below and above the spin-reorientation temperature T SR = 130 K [1,[11][12][13]. Below T SR , where the magnetocrystalline anisotropy of Nd sub-lattice is dominant, the insertion of the more electronegative N atom at the (0, 0, 1/2) position of the ThMn 12 structure introduces a positive contribution to the inherently negative second-order crystal field parameter (A • 2 ), so that the total magnetic anisotropy becomes axial for RE with a negative second-order Stevens factor (α J < 0), such as Nd.…”

“…(ii) The increase of the axial anisotropy at T > T SR after nitrogenation affects the saturation behavior of λ so that in spite of the host compound characteristics, the anisotropic magnetostriction of nitride slowly increases when increasing the applied field even up to μ 0 H = 1.5 T. (iii) The very small magnitude of the λ of hydride sample at T < T SR sounds reasonable considering that the range of fields we can apply (1.5 T) is large enough to rotate effectively the magnetization axis of the hydride taking into account the increased anisotropy field of the Nd sub-lattice. (iv) The decrease of the saturation value of λ at T > T SR originates from the lowered magnetic anisotropy and saturation magnetization upon hydrogenation with respect to that of host compound [11][12][13][14]. Here, it is worth to note that the volume magnetostriction of NdFe 10 V 2 N x is negligible for applied fields below 0.6 T. At room temperature, the volume magnetostriction of NdFe 10 V 2 N x is similar to that of host compound, with a minimum around μ 0 H = 0.9 T, while the magnitude of the volume magnetostriction of the hydride increases linearly by increasing the applied field.…”

Structure and magnetic properties of TbFe11−xMnxTi compounds

“…This phase can be stabilized by replacing some of the iron atoms with a small amount of other elements such as Ti, V, Mn, Co, Mo, Nb, Si, Al, etc., and the RFe 12−x M x metallic compounds can be obtained. Some of the compounds of the type RFe 12−x M x are characterized by fairly high values of the Curie temperature, saturation magnetization and magnetocrystalline anisotropy [1][2][3][4][5]. So the iron-rich rare earth transition-metal compounds become new potential candidates for permanent magnet applications, and the study of these compounds is attracted intensively worldwide.…”