Human somatosensory evoked magnetic fields (SEFs) have been measured in a nonmagnetically shielded room with a SQUID connected to a second order gradiometer. The median nerve of the right wrist was stimulated electrically. Magnetic fields perpendicular to the surface of the head of 500 samples were measured over 25 positions and were averaged with a bandpass filter of 1 to 30 Hz. In order to estimate the equivalent current source in the brain a 3-D ECD (equivalent current dipole) technique was introduced in the meaning of the best fit between experimental and theoretical distribution. The calculated ECD of a latency of 90 ms was located at the Rolandic fissure of the left hemisphere where the sensory area related to the finger is located. The calculated ECD was 1.53 nAm and the depth was 2.5 cm from the surface of the head. The direction of the ECD was almost perpendicular to the Rolandic fissure and it extended from the sensory to the motor area.

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  When a TbFe layer is so thin that the incident light transmits through several TbFe layers in a TbFe/SiO compositionaliy modulated film, a multi-reflection occurs at each interface. Kerr rotation angle can be strongly enhanced by the interference of these reflected lights. Kerr rotation angle runs up to 12 degrees at a wavelength of light of 6328Å. A large enhancement of Kerr rotation angle is attained at an arbitrary wavelength of visible light by selecting the thickness of each layer. The perpendicular magnetic anisotropy is dominant in a TbFe/SiO compositionaliy modulated film even when the thickness of a TbFe layer is 39Å because of magnetostriction at interfaces. In a compositionaliy modulated film, optical constants of a magnetic thin film, but not of a coating layer, can be tuned to the antireflection whithout quenching the perpendicular magnetic anisotropy.

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  The magnetization response of a thin film head was studied using high-frequency micro-Kerr system. This system has a frequency response up to 50 MHz and is able to measure magnetization changes. A laser spot size is about 0.5μm in diameter. An amplitude of magnetization changes at the center of the pole increased as a frequency increased, though it was not so at an edge of the pole. A phase shift at the edge of the pole is larger than that at the center of the pole. These phenomena seem to be caused by the eddy current distribution of the magnetic pole.

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