Abstract
The low temperature phases of Na2Ti3Cl8 and their phase transitions were investigated by powder neutron diffraction, heat capacity, and magnetic susceptibility measurements between 1.6 K and room temperature. Aside from the previously known high temperature α-phase (R3m) and low temperature γ-phase (R3m), a new intermediate temperature β-phase was detected. It has a k = (1/4,1/4,0) superstructure and its molar volume and χT product are half way between the α- and γ-phases. The β-phase is observed between 210 K and 190 K on cooling in powder samples. Its formation is kinetically hindered in crystals. Upon heating the β→α transition occurs at 227 K. From the γ-phase, a γ→α transitions is observed on heating. Only in heat capacity measurements, a shoulder of the peak indicates an intermediate formation of the β-phase. Strong antiferromagnetic interactions between the Ti2+ ions result in the formation of triangular trimers (Ti3 clusters). In the γ-phase all Ti2+ ions are part of trimers. For the β-phase a structural model is proposed, where half of the Ti2+ ions form trimers. No long-range magnetic order was observed in Na2Ti3Cl8 down to 1.6 K.
Original language | English |
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Pages (from-to) | 2063-2069 |
Number of pages | 7 |
Journal | Zeitschrift fur Anorganische und Allgemeine Chemie |
Volume | 643 |
Issue number | 23 |
DOIs | |
State | Published - Dec 13 2017 |
Funding
This work is partially based on experiments performed at the Swiss spallation neutron source (SINQ), Paul Scherrer Institute (PSI), Vil-ligen, Switzerland. We thank Daniel Biner, DCB Bern, for technical support. The financial support by the Swiss National Science Foundation grant No. 200020_150257 is gratefully acknowledged.
Keywords
- Chlorides
- Kagome lattice
- Phase transitions
- Sodium salts
- Titanium