SPring-8, the large synchrotron radiation facility

Date : 16:00 - June10, 2008

Place : Kamitsubo Hall

Speaker : Roberto Boada

Affiliate : ICMA, CSIC-University of Zaragoza, Spain

Title : Impact of Aluminium on the magnetic properties of the RT2 compounds ( R = rare earth, T = transition metal ) through the modification of the electronic structure

Abstract :
To provide insight into the effect of the Aluminium on the magnetic properties of the R-T intermetallic systems, a study of XAS and macroscopic magnetic measurements of the R_1-x R'_x (Fe_1-y Al_y )₂ Laves Phase compound has been done.

The substitution of the magnetic rare-earth (R= Ho, Er) by a non-magnetic one (R'= Y, Lu) acts as a simple dilution effect of the rare-earth sublattice magnetization and it has little influence in the magnetic ordering temperatures. By contrast, when Al replaces Fe the ferromagnetic behaviour of the material is seriously affected leading to the breakdown of the long magnetic ordering and to the appearance of spin-glass behaviour.

The XAS study at different absorption edges (Fe K-edge and at the rare-earth L1 and L3 edges) provides the disentangling of the structural and electronic changes induced by the different substitutions. Hence, a special discussion is deserved to the way in which this substitution modifies the R(5d)-T(3d) hybridization which governs the R-T interaction and, consequently, the magnetic properties of the systems under study. The obtained results reveal that the change of the magnetic properties upon Al substitution are triggered by the strong modification of the density of states (DOS) which also affects the R(5d)-Fe(3d) hybridization.

OUTLINE :
• Introduction:
 - Laves Phase compounds (RT₂)
 - Synthesis (arc melting and annealing process)
 - Powder XRD characterization (Rietveld refinement)
• Magnetic measurements (SQUID magnetometer): M(H,T)
• XAS measurements (BM25 – SpLine, ESRF):
 - Fe K-edge
 - Rare-earth L_1,3-edge

Organizer : Suzuki Motohiro (PHS:3871)