R. Rani

High-energy product ThMn12 Sm-Fe-T and Sm-Fe permanent magnets synthesized as oriented sputtered films

Binary SmFe12 and Sm(Fe,T)12 films, where T =Ti and V, crystallized into the ThMn12‐type structure, have been synthesized as sputtered films such that the c axes of the crystallites are oriented perpendicular to the film plane. It has been possible to synthesize Sm(Fe,T)12 films which exhibit a very dominant (002) texture with intrinsic coercivities of 5 or more kOe. Such films exhibit flux densities 4πMs of more than 10 kG perpendicular to the film plane. No discernible columnar structure is exhibited so that the static energy product measured perpendicular to the film plane is nearly 21 MGOe.

Fully in plane aligned SmCo based films prepared by pulsed laser deposition

SmCo based films, ≈1–3 μm thick, have been directly crystallized onto moderately heated polycrystalline susbstrates, 375 °C, by high pulse energy pulsed laser deposition. Films have been deposited to compare shadow and direct deposition. Only for shadow deposition conditions has it been possible to deposit CaCu5-type structure films that exhibit hysteresis loops characteristic of single phase materials with high coercivities. The shadow deposited films are mirror-like, very fined grained (less that 0.2 μm), and with the crystallite c axes completely aligned onto the substrate plane. For optimally deposited films, room temperature hysteresis loops measured perpendicular to the film plane were closed with approximately zero coercivity. For such films, hysteresis loops measured in plane with fields to ±90 kOe at room temperature exhibited intrinsic coercivities of at least 22.5 kOe. Measurement fields of ±19 kOe yielded only minor loops that did not enclose the origin in some cases. The fully textured SmCo b...

HIGH COERCIVITY SMCO BASED FILMS MADE BY PULSED LASER DEPOSITION

Films of SmCo based materials exhibiting high intrinsic coercivities and smooth hysteresis loops have been prepared by pulsed laser deposition (PLD) onto moderately heated substrates. Films directly crystallized from SmCo5 targets onto 375 °C substrates exhibited a maximum iHc=11.3 kOe at a pulse repetition rate of 10 Hz with lower coercivities for both lower and higher pulse repetition rates. In the present case the films were deposited onto polycrystalline substrates. The films exhibited a very small grain size of less than 1 μm diameter, were mirrorlike, and shadow deposited films were relatively particulate free under scanning electron microscope examination. Shadowed PLD deposition was used for the best films. Laser wavelengths of 193 and 248 nm were used with pulse repetition rates from 5 to 50 Hz. Films grown without shadowing exhibited a great deal of particulate contamination. The hysteresis loops of such nonshadowed films were constricted and exhibited drops in the 4πM values upon demagnetizatio...

Cell volume expansion in Sm5(Fe, T)17, T = Ti, V, magnetic phases

Abstract The formation of binary Sm5Fe17 is reported for the first time. The room-temperature i H c observed was 7 kOe. It is also shown that V and Ti replacements for approximately 10% of the Fe yield a systematic and expected expansion of the unit-cell volume. This is interpreted to mean that the Ti and V are replacing part of the iron in the primary magnetic phase.

High coercivity Sm2Fe17Nx and related phases in sputtered film samples

High coercivity film samples of the ordered Sm2Fe17Nx phase with intrinsic coercivities, iHc, up to 23 kOe at 293 K, and 35 kOe at 10 K, were synthesized by rf sputtering. Random orientation Sm2Fe17 films were formed by the subsequent crystallization of originally amorphous deposits. The iHc of the original Sm2Fe17 films was 0.75 kOe at 293 K. X‐ray diffractometer traces from 2Θ=28° to 73°, CuKα, exhibited 14 lines. Before nitriding all 14 lines were fit to the 2–17 rhombohedral structure with a=8.555 A, c=12.445 A, with a weighted root‐mean‐square deviation in 2Θ of 0.01°. After nitriding the cell volume increase was ≊7%. Nitriding of the ordered 2–17 films had to be performed in a very narrow temperature range to optimize the magnetic properties. The best magnetic properties were obtained by crystallizing the amorphous deposits in situ at a temperature of ≊900 K for 1 h and then subsequently nitriding in N2 gas at 0.75 atm., at 675–725 K, for 2 h. The room temperature coercivity as a function of the Sm ...

High anisotropy Nd(Fe,T)12Nx, T=Ti, Mo, films and disordered RE(Fe,Ti) phases before and after nitriding

Highly textured thin films, of ordered Nd(Fe,T)12, T=Ti, Mo, and disordered Nd(Fe,Ti)7 phases, were synthesized by rf sputter deposition. The 1–12 films were highly (002) textured with the c axes oriented perpendicular to the film plane. The disordered Nd‐Fe‐Ti films were fitted to the disordered TbCu7 phase and could be made highly (110) textured with the c axes randomly distributed in the film plane. Nitriding was carried out in N2 at P=400 Torr at ≊450 °C for 2 h. The room‐temperature magnetocrystalline anisotropy fields of the NdFe11Ti and NdFe11Mo films, which were uniaxial, were 10 and 5 kOe, respectively. After nitriding the NdFe11TNx films remained uniaxial, but the anistropy fields increased to 108 and 130 kOe for Ti and Mo, respectively. The iHc perpendicular to the film plane of NdFe11T increased to 5.3 kOe, T=Ti, and to 7.2 kOe, T=Mo, after nitriding. At 293 K, the highest‐energy product of 30.2 MGOe was obtained for a T=Mo nitrided sample. The hysteresis loops of disordered Nd(Fe,Ti)7 and Nd(...

Sputter synthesis of TbCu7 type Sm(CoFeCuZr) films with controlled easy axis orientation

Single phase TbCu7 type films of Sm(CoFeCuZr) have been sputter synthesized for a range of sputter gas pressure, deposition temperature, and two different gas species: Ar and Ar50%Xe. The magnetic and crystallographic properties of these films as a function of sputter deposition parameters have been studied. Films synthesized at temperatures near their crystallization temperatures at sputter gas pressures exceeding 60 mTorr of Ar50%Xe, had a strong c‐axis in‐plane texture. The remanent magnetization ratio for measurement perpendicular to the film plane versus in plane was close to zero for such films. X‐ray diffraction patterns of these films showed only (hk0) type reflections. At gas pressures around 30 mTorr predominant reflection was (111) type. The perpendicular to the in‐plane BR ratio for such films was around 0.55. For films with in‐plane c‐axis texture, in‐plane Br of 9.0 kGauss and coercivities in the range 3–10 kOe were possible. Pressures of Ar and Ar50%Xe correlated roughly in the ratio 1:2 fo...

Film synthesis and magnetic properties of ThMn12‐type Sm(Fe1−xTx)12, x≤0.12

Films of binary SmFe12 and Sm(Fe1−xTx)12 compounds, where x≤0.12, and T=V, V‐Ti, and Ti, exhibiting the ThMn12‐type tetragonal crystal structure have been successfully synthesized. These films were crystallized by rf sputter deposition onto Al2O3 substrates preheated to 400–550 °C. The lattice parameters of the SmFe12 tetragonal structure, x=0, were determined to be a=8.438±0.005 A and c=4.805±0.005 A. The binary SmFe12 and Sm(Fe,T)12 alloys were found to be magnetically uniaxial as confirmed by magnetization measurements, x‐ray diffraction, and Mossbauer spectroscopy. Coercivities up to 6 kOe were obtained for these films. For the binary system, room‐temperature 4πM values of 14.3±0.2 kG were obtained for magnetization measurements made perpendicular to film plane at applied fields of 90 kOe. For the first time, remnant flux‐density values close to the saturation values were obtained for x≤0.08 for films synthesized with an extreme (002) texture. For certain dense films a static energy product of 21 MGOe...

Controlled synthesis of differently textured Sm(Fe, Ti)/sub 12/ sputtered films

It was shown that Sm(Fe/sub 1-x/Ti/sub x/)/sub 12/, x<or=0.01, film samples can be synthesized systematically with differing crystallite textures to vary the crystallite orientations and the sample coercivities. Texturing can be switched from

Aligned high anisotropy Pr(Fe,Co,Mo)12N film samples

Highly aligned (002) textured sputtered films of Pr(Fe12−y−zCoyMoz)Nx, where y=0–2.5, and z=0.4–1.0 compounds have been successfully synthesized. Before nitriding, the films exhibited nonuniaxial soft magnetic properties with room temperature coercivities of 0.70 kOe. A profound change of magnetocrystalline anisotropy occurred on nitriding. X‐ray diffraction traces showed that the ThMn12‐type tetragonal structure was retained with a saturating increase in cell volume over the first 15 min of nitriding time at 750 K. The coercivity, however, reached a maximum for a nitriding time of 25 min at 750 K. Samples nitrided for times greater than ≊25 min were taken as fully nitrided with ≊1 N per ThMn12 formula unit. The samples slightly richer in Pr showed somewhat higher coercivity perpendicular to the film plane as compared to stochiometric Pr(Fe,Co,Mo)12N films. From high field measurements to 80 kOe, the maximum room temperature coercivity perpendicular to the film plane was 9.4 kOe, which rose to 22.0 kOe at...