Magnetic structures and transitions of GdNiSi3 and TbNiSi3

Author(s)

Rodolfo Tartaglia Souza

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2019-03-29

Examining board members

Eduardo Granado Monteiro da Silva; Raimundo Lora Serrano; Carlos Rettori

• Advisor: Eduardo Granado Monteiro da Silva

Abstract

In this work, we solved the magnetic structures of GdNiSi3 and TbNiSi3 by means of resonant magnetic x-ray diffraction experiments. These compounds are members of the family RNiSi3 (R = Y, Gd-Lu), that presents an interesting antiferromagnetic ground state at low temperatures (TN= 2-32 K) evolving with R and metamagnetic transitions under applied magnetic field for some of the compounds. In our measurements on both Gd and Tb based-compounds, we found that the primitive magnetic unit cell matches the chemical cell below the Néel temperatures TN = 22.2 and 33.2 K, respectively. The magnetic structure features ferromagnetic layers of Gd/Tb magnetic moments in the ac plane stacked in an antiferromagnetic + - + - sequence along the b axis, with magnetic moments along the a direction (magnetic space group Cmmm¿), which contrasts with the + - - + stacking sequence and magnetic moments towards the b direction previously reported for YbNiSi3. This indicates a change in the coupling between second-neighbor as we move from Gd and Tb to Yb. We also observed that GdNiSi3 and TbNiSi3 shows a magnetoelastic expansion of the b lattice parameter upon cooling below TN, indicating that the + - + - coupling stabilizes the magnetic structure under this expansion (AU)

• FAPESP's process: 17/04913-1 - Structures and Magnetic Transitions in RNiSi3 (R:Gd-Ho)
• Grantee: Rodolfo Tartaglia Souza
• Support Opportunities: Scholarships in Brazil - Master