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Volume 24, Issue 4_1
Displaying 1-4 of 4 articles from this issue
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Contributed Paper
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J. Sugawara, E. Nakashio, S. Onoe, S. Kumagai2000 Volume 24 Issue 4_1 Pages 192-195
Published: 2000
Released on J-STAGE: February 26, 2007
JOURNAL OPEN ACCESSThe annealing effect of ferromagnetic tunnel junctions was studied so as to achieve a higher MR ratio for the junction of an NiFe/CoxFe1-x/Al-O/CoxFe1-x/IrMn system. We fabricated NiFe/Co90Fe10/Al-O/Co90Fe10/IrMn junctions (sample 1) using metal masks. Rs increased monotonically with increasing annealing temperature. The MR ratio increased up to 300°C and rapidly decreased as a result of annealing at higher temperatures. The barrier height (φ) increased and the barrier width (d) decreased with increasing annealing temperature. It is thought that a suitable Al-O barrier was formed by annealing and that the MR ratio increased as a result. To obtain more data, we measured the saturated magnetization (Ms). Ms decreased rapidly as a result of annealing over 300°C: this corresponds to the rapid decrease in the MR ratio. Next, we fabricated NiFe/Co75Fe25/Al-O/Co75Fe25/IrMn junctions (sample 2) without breaking the vacuum in the stacking process. The maximum MR ratio.was 49% after annealing at 200°C. The annealing temperature dependence of samples 1 and 2 were quite different.View full abstractDownload PDF (310K) -
H. Kanekiyo, S. Hirosawa2000 Volume 24 Issue 4_1 Pages 196-201
Published: 2000
Released on J-STAGE: February 26, 2007
JOURNAL OPEN ACCESSThe effect of co-addition of Cr and Co to Fe3B/Nd2Fe14B exchange-spring nanocomposite permanent magnets on the magnetic properties and their stability was investigated. It was found that HcJ of Fe3B/Nd2Fe14B exchange-spring magnets can be controlled in the range from 300 kA/m to 600 kA/m by adjusting the Cr and Nd concentrations. The squareness of the demagnetizion curves is improved by simultaneous addition of Cr and Co. Thermal stability is also improved by Cr addition: irreversible flux losses rate of the 5 at% Cr-doped Fe3B/Nd2Fe14B exchange-spring magnets were about 1 % after exposure to a temperature of 100°C. This type of magnets are less susceptible to oxidation because the rare-earth content is lower than that of conventional Nd2Fe14B isotropic powders. The higher packing density can be obtained because of the round shape of the pulverized Fe3B/Nd2Fe14B exchange-spring magnet. Consequently, Fe3B/Nd2Fe14B exchange-spring magnet powders are suitable for the injection-molding process in which the magnetic powders are exposed to high temperatures.View full abstractDownload PDF (422K) -
T. Fujiwara, H. Fujii, T. Shigeoka2000 Volume 24 Issue 4_1 Pages 202-207
Published: 2000
Released on J-STAGE: February 26, 2007
JOURNAL OPEN ACCESSIn this paper, we report experimental results on the overall magnetic properties of intermetallic compounds Gd1-xLaxMn2Ge2 (0≤x≤1.0) with a ThCr2Si2-type layered structure. In GdMn2Ge2, a first order transition was observed from antiferromagnetic to ferrimagnetic state at Tt3 below TN with decreasing temperature, while in Gd1-xLaxMn2Ge2 with x = 0.075 and 0.050, two kinds of first-order transitions, from ferrimagnetic to antiferromagnetic and from antiferromagnetic to reentrant ferrimagnetic states were observed at Tt2 and Tt3 after they become ferrimagnetic below Tt1. As x further increases canted ferrimagnetism appears with a compensation temperature in all the ordering temperature regions for 0.10 < x < 0.40, whereas no compensation behavior was observed for x > 0.50. The compensation behavior as a function of temperature is discussed on the basis of the two-sublattice molecular-field model.View full abstractDownload PDF (462K) -
T. Fujiwara, H. Fujii, H. Fukuda, T. Shigeoka2000 Volume 24 Issue 4_1 Pages 208-213
Published: 2000
Released on J-STAGE: February 26, 2007
JOURNAL OPEN ACCESSIn this work, we studied the magnetic and transport properties of an intermetallic compound Gd0.925La0.075Mn2Ge2 with a ThCr2Si2-type layered structure. Gd0.925La0.075Mn2Ge2 exhibits canted ferrimagnetism with ferromagnetic and antiferromagnetic components below Tt1 = 348K. With decreasing temperature, it moves into a non-collinear antiferromagnetic state at Tt2 = 244 K, and finally transforms into a reentrant canted ferrimagnet at Tt3 = 142 K. For Tt3 < T < Tt2, a field induced metamagnetism from antiferromagnetism to ferrimagnetism occurs at relatively lower fields, accompanied with fractal like multi-step metamagnetic transitions, the so called “devil’s stair-case”. The appearance of such fractal like multi-step metamagnetic transitions may result from a step-like formation of ferrimagnetic clusters due to spin-flips of Mn moments that occur independently in the antiferromagnet when magnetic fields are applied as well as from a step-like growth of their ferrimagnetic clusters. In addition, a giant magnetoresistance effect (Δρ/ρ∼15%) was also observed at the metamagnetic transition.View full abstractDownload PDF (460K)
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