Tailoring the magnetism of Tb5Si2Ge2 compounds by La substitution

Journal Article · Sun Jan 01 00:00:00 EST 2012 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.86.014403· OSTI ID:1051472

Belo, Joao ^[1]; Pereira, Andre ^[1]; Araujo, Joao Pedro ^[1]; Dela Cruz, Clarina R ^[2]; Moreira Dos Santos, Antonio F ^[2]; Goncalves, Joao Nuno ^[1]; Amaral, Vitor ^[3]; Morellon, Luis ^[4]; Ibarra, M. Ricardo ^[4]; Algarabel, Pedro A. ^[4]; Magen, C ^[5]

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1. University of Porto, Portugal
2. ORNL
3. University of Aveiro, Portugal
4. University of Zaragoza, Spain
5. Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Zaragoza, 50009 Spain

In order to study the crystal structure, phase relationships, and magnetic properties of the system Tb5-xLaxSi2Ge2, a series of polycrystalline samples with compositions ranging from x = 0 to x = 5 have been synthesized and characterized in detail. At room temperature, two structures have been detected: Compounds in the concentration range 0 <= x < 1 present a monoclinic Gd5Si2Ge2-type structure, while for x > 1 a tetragonal Zr5Si4-type structure is observed. The unit cell volume increases linearly with La concentration but with two different slopes: similar to 18 angstrom(3)/x and similar to 33 angstrom(3)/x for 0 <= x < 1 (monoclinic) andx > 1 (tetragonal), respectively. In the monoclinic region, an increase of T-C was observed, reaching a maximum value of T-C similar to 154 K, at the x = 0.75 composition. This feature is explained based on specific La occupancy at the R2 site which was supported by density functional calculations for low La concentration. The samples that crystallized in the tetragonal structure exhibit a linear decrease of T-C(x) with a slope of partial derivative T-C/partial derivative x similar to -38 K/x, reaching 0 K for the x = 5 composition. A magnetic and structural x-T phase diagram of the Tb5-xLaxSi2Ge2 system in the temperature range 4-300 K is proposed.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1051472
• Journal Information: Physical Review B, Vol. 86, Issue 1; ISSN 1098--0121
• Country of Publication: United States
• Language: English

Related Subjects

Neutron Diffraction
MagnetoCaloric Materials
Tb5Si2Ge2