Magnetostructural phase transitions in ternary rare earth intermetallics
|Andrzej Szytula 1, M. Duraj, Ł. Gondek E. Wawrzyńska,|
1. Jagiellonian University, Institute of Physics (IF UJ), Reymonta 4, Kraków 30-059, Poland
In this work properties of some compounds with the layered crystal structure are discussed. These compounds are in important alternative for delineating fundamental issues concerning transport in 2D magnetic materials. The SmMn2Ge2 crystallizes in the tetragonal ThCr2Si2-type crystal structure which is formed of the monoatomic layers along the c-axis with the following sequence Sm–Ge–Mn2–Ge. Magnetic data indicate complex magnetic properties. With decreasing temperature the change of the magnetic properties with the following sequence: antiferro- (between 385 and 341 K), ferro- (341–153 K), reentrant antiferro- (153–106.5 K) and reentrant ferro- (below 106.5 K) magnetic behavior is observed. Temperature dependence of the lattice parameters a and c shows the jump of these parameters equal Δa≈0.2 % at T1=106.5 K and T2=153 K and Δc≈0.02 % at T1 and ~0.06 % at T2. In these temperatures also the change of the electrical Δρ/ρ≈0.056 at T1 and 0.05 at T2 and magnetoresistivity 3.2 % at T1 and 5.4 % at T2 is observed. It was suggested that due to the layered arrangement of the Mn layers in this compound an analogy to GMR effects in artificial magnetic multiplayer systems exists. This problem is discussed on the other isostructural compounds. Nd3Mn4Sn4 crystallize in the orthorhombic layered structures of Gd3Cu4Ge4. Magnetic and neutron diffraction data give that this compound is antiferromagnet with TN1=210 K. Below TN1 Mn moments form a collinear magnetic structure. Below
TN2=60 K the Nd moments also order and form collinear magnetic structure while the magnetic order of the Mn moments remains unchanged. The temperature dependence of lattice parameters a, b and c and unit cell volume V indicates a positive sign of the magnetostriction at TN2 and negative sing at TN1.
In TbRhSi the change of the magnetic structure is connected with the change of the lattice parameters.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium B, by Andrzej Szytula
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-17 06:59 Revised: 2009-06-07 00:44