MAGNETIC PHASE-TRANSITIONS IN THE SYSTEM LA(FE,CO,AL)13 AT HIGH-PRESSURES

The magnetic properties and electrical resistivity of La(Fe0.88-xCoxAl0.12)13 alloys (0.009 < x < 0.14, cubic symmetry) have been studied under hydrostatic pressures of up to 18 kbar. The ferromagnetic-paramagnetic transitions (x > 0.01) and ferromagnetic-antiferromagnetic-paramagnetic transitions (x < 0.01) in the course of heating were studied at both ambient and high pressure. The action of pressure on the magnetic phase transitions is qualitatively similar to a decrease of cobalt concentration in the La(Fe0.88-xCoxAl0.12)13 alloys. Applying pressure results in a decrease in the magnetic phase transition temperatures. For alloys with concentrations in the vicinity of the AF-F transition (x = 0.02-0.04) antiferromagnetic features were observed to occur under pressure. The results are discussed in the context of the instability of the ferromagnetic state in this Invar system.