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The revival of multiferroics is motivated by their exciting physics and their ability to bring novel functionalities to a number of technological fields such as spintronics. The lack of room temperature ferroelectric ferromagnets is a problem and has driven most of the attention thus far to BiFe[O.sub.3], a ferroelectric weak-ferromagnet with both transition temperatures superior to 300K. In this paper, we report on the properties of BiFe[O.sub.3] heterostructures and focus on two types of approaches towards BiFe[O.sub.3]-based spintronics devices. One uses BiFe[O.sub.3] as an exchange bias layer in spin-valve structures in which the magnetic configuration is potentially switchable by an electric field, via the magnetoelectric coupling existing in BiFe[O.sub.3]. The other consists in integrating BiFe[O.sub.3] ultrathin films as tunnel barriers in magnetic tunnel junctions with the objective of exploiting their ferroelectric character along with their specific symmetry filtering properties. General perspectives for multiferroics in spintronics are given. Index Terms--Exchange bias, multiferroics, spintronics, tunneling.

We describe a thermal magnetic noise simulation of tunneling magnetoresistive (TMR) heads. We calculate the phase and amplitude distributions of the local noise resistance derived from the magnetization fluctuation of the free layer in the several gigahertz range and consider their relations with the magnetic noise spectrum. The results show that the phase distribution of the noise resistance strongly influences the second or higher resonant peaks in the magnetic noise spectrum of TMR heads. As an example, we show that the second resonant peak appears in the spectrum when the asymmetric magnetic field is applied to the free layer. Index Terms--Magnetic noise, tunneling magnetoresistive (TMR) head.