68th Magnetic Materials Center Seminar
February 21, 2008, 9:00-
8th floor middle seminar room, Sengen
INTRINSIC and EXTRINSIC magnetic properties of highly perpendicular anisotropic NdFeB thin films
K. Suresh
NdFeB thin films were fabricated using sputtering on MgO(100) and thermally oxidized Si substrates with Ta buffer layer. The substrates were held at elevated substrate temperatures during sample preparation. Subsequently, the films were characterized using XRD, TEM , VSM and SQUID magnetometer for structural as well as magnetic property evaluation. The results showed that
(1) formation of NdFeB single phase with strong (00l) texture perpendicular to the substrate plane,
(2) excellent combination of hard-magnetic properties (Ms : 12kG, Mr/Ms : ~1, Hc: 1.23 kOe and (BH)max : 34 MGOe) with high magnetic texture (Mr(IP)/Mr(OP)~0), a like sintered bulk magnets.
In this presentation, intrinsic and extrinsic magnetic properties of NdFeB (50nm) thin films combined with microstructural information would be presented.

Effect of optimal heat treatment on morphology and coercivity of the Nd-Fe-B sintered magnet
N. Hase
As you know, the Nd-Fe-B sintered magnet has the largest (BH)max. Then, in recent years, this magnet has been hoped to apply to high T applications. But, the Hc of this magnet decreases rapidly with increasing T. For this reason, the addition of Dy etc. plays a crucial role for securing the enough Hc at high T. From recent experiments, I'll try to explain about the mechanism of the Hc enhancement from a view of behavior of additional elements(Dy,Cu) during the optimal heat treatment.

Giant magnetoresistance effect (GMR) of spin valve structure with top-pinned amorphous-CoFeB /IrMn
C. Y. You
The work I will present in this seminar originates from one idea of interface tailoring of GMR or TMR stacks using amorphous CoFeB. Because of their high resistivity and low anisotropy, amorphous materials are also promising candidates for the sense layers in practical GMR sensors. However, it was reported in literatures that exchange bias cannot be obtained from top-pinned amorphous-CoFeB/IrMn structure. Luckily, the exchange bias from top-pinned amorphous-CoFeB/IrMn structure was realized in our machine. A promising CIP-GMR (~1.5%) was achieved from the simple CoFeB/Cu/CoFeB/IrMn/Ru stacks.