Spin glass transitions in the absence of chemical disorder for the pyrochlores A2Sb2O7 (A=Mn, Co, Ni)

✍ Scribed by H.D. Zhou; C.R. Wiebe; J.A. Janik; B. Vogt; A. Harter; N.S. Dalal; J.S. Gardner

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 902 KB
• Volume: 183
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2010.01.025

✦ Synopsis

The pyrochlores in the series A 2 Sb 2 O 7 have been synthesized and characterized as exhibiting spin glass transitions at T SG = 41, 4.5, and 2.6 K (for A=Mn 2 + S ¼ 5 2 , Co 2 + S ¼ 3 2 and Ni 2 + S =1, respectively) despite the lack of chemical disorder. Since the Curie-Weiss temperature remains essentially constant for all members in the series (y $ À40 K), the frustration index for these materials increases significantly as the moment size is reduced from f ¼ jyj=T SG ¼ 1:1 (Mn 2 + ), to 9.3 (Co 2 + ) to 14.6 (Ni 2 + ). There is also a corresponding change in the spin dynamics measured by the shift in the AC susceptibility signal as a function of frequency. These new materials provide an avenue to investigate the effect of quantum fluctuations on the Heisenberg pyrochlore lattice in the low spin limit, and show there is a dramatic change in the spin dynamics as the quantum regime is approached.