Lin‐Yuan Yang

Structural, magnetic and magnetostrictive studies of Tb0.27Dy0.73(Fe1 − xAlx)2

Abstract Measurements of magnetic properties, X-ray diffraction and magnetostriction were made on Tb 0.27 Dy 0.73 (Fe 1 − x Al x ) 2 ( x = 0.1, 0.2, …, 0.7) compounds. It was found that the system has the cubic MgCu 2 structure over almost the whole (Fe,Al) concentration range investigated, except for a narrow intermediate range ( x = 0.4–0.6) where the hexagonal MgZn 2 structure appears. With increasing Al content x , the lattice constant a increases linearly with x . The first replacement of Fe results in a marked decrease in the Curie temperature, which is followed by a slight decrease in T C with x . A linear decrease in magnetostriction of | λ | − λ ⊥ | at room temperature with x was also observed from 1530 × 10 −6 for x =0 to 36×10 −6 for x =0.3. The saturation magnetization σ s exhibits a complex concentration dependence in the Tb 0.27 Dy 0.73 (Fe) 1 − x Al x ) 2 system: in the range x σ s increases linearly with x and, for x = 0.5–0.6, σ s decreases and then increases again. An enhancement of the magnetic ‘hardness’ in this system was also observed at low temperature.

MAGNETIC AND MAGNETORESTRICTIVE PROPERTIES OF SM1-XDYXFE2 COMPOUNDS AND ITS MOSSBAUER-EFFECT STUDIES

Measurements of x‐ray diffraction, magnetization, magnetostriction, and Mossbauer effect were performed on a series of Sm1−xDyxFe2 samples (x=0, 0.1, 0.15, 0.25, 0.45, and 0.65). It is shown that the system retains the cubic MgCu2 structure over the whole range and the lattice constant decreases linearly with increasing x. Results of Mossbauer effect study at room temperature show that for a small amount of Dy substitution for Sm, x<0.15, easy axes of the magnetization keep in the [111] direction. For x≳0.15, the direction of easy axes rotates gradually from [111] for x=0, and 0.1 to [100] for x=0.45 and 0.65. The concentration dependence of the saturation magnetization exhibits a minimum at x=0.30 for 1.5 K and at x=0.45 for room temperature, reflecting the occurrence of the compensation of magnetic moments at various Sm/Dy ratios. For x=0.45 and 0.65, the pinning phenomenon of narrow domain walls was observed at low temperature. The magnetostriction was found to decrease with the increase in the Dy cont...

Hard magnetic properties in melt‐spun Co82−xFexZr18 alloys

The Co82−xFexZr18 (0≤x≤16) alloys melt‐spun with vs=40‐47 m/s exhibit a single phase for all x. The Curie temperature Tc and the room‐temperature saturation magnetization σs increase monotonically with increasing Fe concentration x. The anisotropy field for x=0 is found to be about 3.13T. In the as‐quenched samples at the optimal quenching rate, room‐temperature coercive field Hc decreases almost linearly from 3.0 kOe for x=0 to 1.3 kOe for x=16. The maximum energy product (BH)max increases at first with increasing Fe concentration x, and goes through a maximum value of 4.2 MGOe at about x=5, then decreases with x.

Pressure effects on the stability of magnetic structure of Mn3Zn1−xGexN (x=0,0.1)

This paper reports that the pressure effects on the electronic transport properties of Mn3ZnN and Mn3Zn0.9Ge0.1N were measured under pressures up to 2.4 GPa. Cooling and warming cycles of the temperature-dependent magnetization curves of Mn3ZnN show a hysteresis phenomenon near the transition, implying a first order transition. The cracks which appear in the vicinity of magnetic transition at ambient pressure for Mn3ZnN and at applied pressures not more than 0.3 GPa for Mn3Zn0.9Ge0.1N are restrained under higher pressures. The paramagnetic-antiferromagnetic transition temperature TN decreases almost linearly at the rate of 1.9 and 51 K/GPa for Mn3ZnN and Mn3Zn0.9Ge0.1N respectively, which is explained by the model of TN discussed by Fruchart and the Labbe–Jardin tight-binding approximation model.

Magnetic properties and crystallization of amorphous Fe‐Nd‐B alloys at constant Nd concentration

The B‐content dependence of magnetization, Curie temperature, and crystallization temperature for amorphous (Fe1−xBx)100−yNdy alloys with y=4, 7, and 12 were studied. Spontaneous magnetization shows a monotonic decrease with x, and the noncollinear spin structures have been proposed to explain the observed results. It is found that the Curie temperature of the samples increases at first with increasing B concentration x, and shows a maximum value at a certain B concentration, then decreases monotonically with x. The composition dependence of Tc is explained by the average molecular‐field model. An exceptionally strong rise of crystallization temperature with x is found, and demonstrates that the thermal stability of amorphous Fe‐Nd‐B alloys has a remarkable enhancement by the substitution of B for Fe.

Influence of quenching rate and heat treatment on the magnetic properties and phase components of rapidly quenched Fe77.5Nd4B18.5 alloy

Abstract The magnetic properties and phase components of rapidly quenched Fe77.5Nd4B18.5 alloy as a function of quenching rate and heat treatment were studied. X-ray diffraction and thermomagnetic measurements show that the Fe77.5Nd4B18.5 ingot consists of Nd2Fe14B, Fe2B and α-Fe. The X-ray diffraction patterns of optimally annealed samples show only metastable Fe3B phase which decomposes into Fe2B and α-Fe at Ta > 850 °C, but the thermomagnetic curves show the presence of the Nd2Fe14B phase. In the sample annealed at 950 °C for 60 min, Nd1.1Fe4B4 appears in coexistence with Nd2Fe14B, Fe2B and α-Fe. The Fe77.5Nd4B18.5 alloy is found to have very good glass-forming ability. Samples prepared at quenching rates vs ⩾ 6.6 m s−1 are amorphous and magnetically soft. Annealing at about 650–670 °C gives the highest coercive field, which is nearly independent of quenching rate.

Magnetic properties of amorphous Co98-xZrxB2 alloys before and after crystallization

Abstract The glass formability and magnetic properties of rapidly quenched Co 98− x Zr x B 2 alloys were studied. The crystallized samples are found to have a good hard magnetic property. The coercivity H c and energy product ( BH ) max depend strongly on the quenching rate and annealing temperature. The highest room-temperature H c and ( BH ) max in the optimal heat-treated samples are obtained to be 3.7 kOe for x = 17 and 4.5 MGOe for x = 16, respectively.

The structural transition and magnetism of the Al65Cu20Fe15 quasicrystal

Al65Cu20Fe15 is a thermodynamically stable quasicrystal. There are two kinds of quasicrystal present in such a material: 3D quasicrystal-icosahedral (I phase) and 2D quasicrystal-decagonal (D phase). The I phase is dominant in rapidly quenched samples and exhibits Pauli paramagnetism. For annealed samples, however, the D phase becomes dominant and exhibits diamagnetism. Macrostructural transitions from the I phase to the D phase during annealing were observed by SEM. The results of UPS experiments show a gradual increase in Fermi energy implying that the unfilled energy level of Fe is being filled by conduction electrons during such a structural transition. This causes the magnetism to change from Pauli paramagnetism to diamagnetism.

Magnetic properties of rapidly quenched RF/sub e7/Si/sub 6/ alloys

Introduction Since the discovery of S m ( P r ) C q permanent magnet, much effort has been dwoted to substituting iron for cobalt in it. Recently. by means of rapidly quenched method, we got some RFc binary and RFcSi ternary alloys, whose x-ray diffraction lines correspond to that of hexagonal CaCus-type structure. In this paper, we mainly report the magnetic properties of the GdFe7Si, and EtFc7Siz (0 5 I 5 2.5) day systems. Experimental Alloys were prepared by arc melting an appropriate amount of Gd. Er , Fe and SI (purity,99.9%) under high purity argon atmosphere. The melting was repeated several times t o insure homogeneity. Rapidly quenched ribbons were prepared by melting spinning. The substrate surface velocity of the Cr single roller was 47mfe. The x-ray diffraction pattern was recorded using FeK, radiation. The thermomagnetical curve was measured by a magnetic balance in a field of 1.2KOe, and the magnetization at 1.5K was measured by an extracting sample magnetometer in the field range from 0 to 70kOe. Results X-ray diffraction results indicate that five of the GdFe7Si. samples ( z = 0.0. 0.5, 1.0. 1.5, 2.0) and three of the E r F q S i , samples(r = 0.5. 1.0, 1.5) can have the diffraction patterns composed only of the diffraction lines that is associated with the CnCus-type elementary cell. The typical example of the relevant x-ray diffraction diagram is shown in Fig.1. Thermomagnetic curve IM T ) of GdFe7Si1.0 samples is shown in Fig.2. I t is seen that the sample is a single phase. By extrapolating the itp T curve to MZ = 0. the Curie temperature can be determined . Fig.3 summarizes the Curie temperature Tc. of RFerSt, ribbons. I t is evident that a t z = 2.0 for CdFcrSi, and a t I = 1.5 for EtFe,Si., T, have a ma;dmum value. This indicates tha t for the present RFc,Si, systems with the above mentioned x-ray diffraction pattern, the Curie temperature increases with increasing Si concentration. For a kedvalue of z, T, of C d F q S i , is higher than that of EtFe,Si, . this can be understood in view point of the antiferromagnetic coupling between Fe moments and heavy rare earth element moments. Magnetization curves of GdFe7Si, a t 1.5K are shown in Fig.4. With increasing Si concentration, the magnetization decreases. Employing the approach of saturation law, saturation magnetization M . can be determined with the lemt square method. The average magnetic moment on Fe atoms is extracted by asigning R3+ to have free ion d u e of 7 8 s for Gd3+ and 988 for Er3+ respectively. The results are tabulated in Table 1. Obviously, the saturation magnetization per formula unit as well as magnetic moment on iron atoms decrease monotonousiy with i n c r e k g Si concentration.