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This paper presents a magnetic self-power microgenerator with induction planar Cu coil, microspring membrane and a permanent magnet of FePt. A vibratory magnet is fabricated using sputtering process. The induced voltage is simulated using ANSYS software. The size of this microgenerator is as small as 0.45 cm 3 in volume. A maximum energy product ( BH ) max of 40 kJ/m 3 can be achieved after post-annealing process. At exciting 60 Hz frequencies, maximum power 100 μW and voltage 40 mV are induced experimentally. The experimental and simulated results are discussed and compared.

The thermal and magnetic properties of nanocrystalline Fe, CoFe 2 , and Co particles as well as their bulk samples were studied between room temperature and 900°C. From the thermogravimetric analyzer measurements, we have observed that near 200°C an endothermal signal occurs abruptly within 10°C for nanocrystalline Fe, and then this signal decreases with increasing temperature and shows a kink near 550°C. However, an exothermal signal starts near 200°C for nanocrystalline Co and CoFe 2 , and it stops to decrease near 310°C and 440°C for Co and CoFe 2 , respectively. Both endo- and exo-thermal effects near 200°C are related to the aggregation and oxidation of the ultra-fine particles. The kink near 550°C for Fe is related to the Curie temperature of Fe 3 O 4 . The magnetization of the ultra-fine particles was slightly smaller than that of the bulk samples, and it decreased very fast with increasing temperature between 100°C and 200°C. The coercivity of nanocrystalline CoFe 2 is roughly 1780 Oe, and is larger than that of Co ( H c ∼1198 Oe) and Fe ( H c ∼883 Oe). After annealing in air, the content of oxygen in nanocrystalline particles increases roughly to 40% for Fe particles, and roughly to 30% for CoFe 2 and Co particles. The oxidation is manifestly reduced after adding the Co element into Fe nanoparticles.

Recording results of write heads using sputtered laminated FeN/Al/sub 2/O/sub 3/ materials on thin film media with coercivity up to 3800 Oe are compared with those obtained using plated NiFe materials. The thickness of P2 (second pole) of FeN merged write heads is about 3.2 /spl mu/m, and those of plated NiFe heads, 3.5 and 6.3 /spl mu/m respectively. These heads have two write gap thickness, around 0.2 and 0.4 /spl mu/m. Various recording measurements show that these high magnetization FeN heads of 0.15 /spl mu/m gap write well on media of 3800 Oe, while the corresponding NiFe ones with a P2 of twice the thickness could not. For a wide 0.39 /spl mu/m gap, the FeN write heads still work well and the NiFe ones with twice the pole thickness, also did, but at reduced resolution, In short, write heads using a narrow gap and high magnetization materials such as FeN can write 3800 Oe coercivity media, which is capable of storing a bit density over 10 Gb/in/sup 2/. >

By varying the Ga concentrations x of EuTm2Fe5−xGaxO12 from x = 0 to about 0.8, thin magnetic films supporting stable bubbles with diameters from 0.5 to about 8μm, respectively, are deposited epitaxially onto gadolinium gallium garnet substrates oriented (111). For low values of x, the Ga segregation coefficient is about 2 and it decreases slightly as x increases. Thus, films contain roughly twice as much Ga as the LPE fluxed melts in which they grow. Both the characteristic length and magnetic bubble stability factor (Q) increase rapidly with x and, to a lesser degree, so does the uniaxial anisotropy field HA while both 4πM and the uniaxial anisotropy Ku decrease.

Hard bubble suppression with proton and neon implantation was achieved in one micron Eu .8 Tm 2.2 Ga .5 Fe 4.5 O 12 films. The dose and energy required in these one micron bubble films are similar to that required in five micron bubble films, despite the fact that the one micron films have larger uniaxial anisotropy to be overcome with the induced magnetostriction. In addition, controlled state generation (for bubble lattlce device applications) has been demonstrated in the proton implanted samples using two different techniques. The first technique, using a combination of an in-plane field and a critical velocity, is identical to what Hsu has reported with five micron bubbles, except that the in-plane field required in this case is 20 to 40% larger. The second technique, using DC and AC in-plane fields only without any field gradient, has also been shown. In the case of conversion from a bubble that propagates at an angle from the field gradient to one that propagates along the field gradient, a DC in-plane field of 300 Oe is needed. While in the reverse case, an AC in-plane field of 100 Oe or so is necessary.

The (EuTm)3(FeGa)5O12 garnet system is particularly useful in studies of small magnetic bubbles. Physical properties change relatively slowly with the Eu/Tm ratio, and the film composition changes little with isothermal LPE growth conditions. Uniform Eu0.85Tm2.15Fe4.45 Ga0.55O12 films with 1 μm diameter bubbles were grown on 38mm diameter substrates of GGG oriented (111). Using dilute, large volume (100 cc) melts undercooled 25°C and substrates rotated slowly (36 rpm) in a horizontal plane, the collapse field (H0) and thickness are uniform to within 2 percent laterally across films. The temperature stability of H0 and of domain periodicity are good up to 100°C presumably because the films have a high Curie temperature (∠215°C).