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Two series of self-organized hexagonal arrays of uniaxial Permalloy nanowires are grown by electroplating, filling of nanopores in anodic alumina films. Nanowires with periodicities of 65 and 105nm and wire diameter of 25–60nm were investigated by magnetization and ferromagnetic resonance (FMR) measurements. The length of the wires is 2.5μm, the volume ratio 0.13⩽v⩽0.43. A crossover transition from a one-dimensional easy axis “wire” behavior of weakly interacting uniaxial nanowires to a two-dimensional behavior of strongly coupled “wire film” having an easy plane anisotropy is determined from FMR measurements. The crossover occurs at v=0.27 for 105nm periodicity, and v=0.43 for 65nm periodicity. The system of the thinnest nanowires corresponds to a statistical ensemble of weakly interacting uniaxial particles, characterized by the highest coercivity of 1276Oe, the highest switching field distribution, and highest FMR linewidth, resulting from the broad distribution of individual wires. The coercivity monotonously decreases to 440Oe with increasing nanowire radius and volume fraction, as the wire shape anisotropy is reduced and the array anisotropy takes over due to dipolar interwire interaction, smoothing out the individuality of the wires. The behavior of coercivity, switching field distribution, and FMR linewidth is in accordance with the increase of the coupling of the nanowires.

The effect of quasi-hydrostatic pressures up to 100 kbar is investigated on the phase transitions of Fel -a h , alloys by resistivity measurements. The pressure dependence of the first order antiferromagnetic (AF) to ferromagnetic (FM) phase transformation temperature dTk/dp = 4.4 to 6 K/kbar. The pressure dependence of the second order FM to paramagnetic (PM) transition, i.e. that of the Curie-point is dTc/dp = -0.7 K/kbar. At about 60 kbar the thermal hysteresis diminishes, and above the range of the co-existence of three phases (AF-FM-PM) the pressure dependence of the AF-PM transition is characterized by dT/dp = 0.6 to 1.0 K/kbar. The AF-PM transition is investigated in an Ir-substituted alloy (Fe&h4~.&6.5) also, where dT/dp = 0.6 K/kbar.

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