Abstract
A unidirectional anisotropy appears in field cooled samples of dilute magnetic alloys at temperatures well below the cusp temperature of the zero field cooled magnetization curve. Magnetization measurements on a Cu(13.5 at% Mn) sample show that this anisotropy is essentially temperature independent and acts on a temperature dependent excess magnetization, ΔM. The anisotropy can be partially or fully transferred from being locked to the direction of the cooling field at lower fields to becoming locked to the direction of ΔM at larger fields, thus instead appearing as a uniaxial anisotropy. This introduces a deceiving division of the anisotropy into a superposition of a unidirectional and a uniaxial part. This two faced nature of the anisotropy has been empirically scrutinized and concluded to originate from one and the same exchange mechanism: the Dzyaloshinsky-Moriya interaction.
Highlights
A unidirectional anisotropy appears in field cooled samples of dilute magnetic alloys at temperatures well below the cusp temperature of the zero field cooled magnetization curve
Magnetization measurements on a Cu(13.5 at% Mn) sample show that this anisotropy is essentially temperature independent and acts on a temperature dependent excess magnetization, ΔM
The unidirectional anisotropy (Eud) causing exchange biased hysteresis loops in dilute magnetic alloys appears in field cooled samples at temperatures well below the cusp temperature of the zero field cooled magnetization curve[1]
Summary
The sample is a polycrystalline cylinder of Cu(13.5 at% Mn) of height 5 mm and diameter 2 mm with a spin glass temperature of 57 K18. The global homogeneity and composition have been ascertained by EDS (Energy Dispersive Spectroscopy) measurements on different spots of the surface area of the sample and by the sharpness of the spin glass transition at low applied magnetic fields. The experiments are performed in a Quantum Design MPMS XL SQUID magnetometer (5T) and two different PPMS VSM systems (9 T and 14 T). All hysteresis measurements are performed after cooling the sample from a reference temperature, TREF = 70 K
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