Heat capacity of the frustrated magnetic pyrochlores Gd₂Zr₂O₇and Gd₂Hf₂O₇

Abstract

The heat capacities of Gd(2)Zr(2)O(7) and Gd(2)Hf(2)O(7) both show sharp peaks in the vicinity of 0.77 K, consistent with the existence of long range magnetic order. They are superimposed in both cases on broader maxima centered at approximately 1 K, presumably due to short range spin correlations. Both compounds exhibit antiferromagnetic interactions, with Weiss constants of approximately -7 K. Comparisons are made to earlier results for the isomorphic compounds Gd(2)Ti(2)O(7) and Gd(2)Sn(2)O(7).

Magnetic frustration induced large magnetocaloric effect in the absence of long range magnetic order

“…The magnetic entropy (S magnetic ) at T P is found to be only about 60% of R ln 2, suggesting the absence of true long range ordering in the system. The magnetic entropy value reaches saturation value [R ln (2 J  + 1) = R ln 17, with J  = 8] around 60 K, due to presence of spin fluctuation and presence of short range magnetic correlation up to such higher temperature 34 . This is in agreement with the deviation of Curie-Weiss law of inverse susceptibility below 60 K.…”

Relief of frustration in the Heisenberg pyrochlore antiferromagnetGd2Pt2O7

“…The fitted profile describes the data well, giving a goodness of fit, χ 2 , of 1.74. The results of this fit are summarized in Table I [30], Sn [31], Zr [32], Hf [8], and Pb [9], the B-site cation has a closed shell electron configuration. Platinum differs in this regard, with a [Xe]5d 6 valence shell, leading to a filled t 2g orbital and an empty e g orbital.…”

“…This is because gadolinium has a largely isotropic spin only total angular momentum. A number of gadolinium based pyrochlores have now been synthesized and studied, Gd 2 B 2 O 7 with B = Ti, Sn, Zr, Hf, and Pb [6][7][8][9]. Each of these systems undergoes an antiferromagnetic ordering transition at 1 K or lower.…”

Magnetic order in geometrically frustrated Gd2(Ti1−xZrLiao1, Lees2, Baker3 et al. 2011Phys. Rev. B

“…23 We note, however, that Gd 2 Zr 2 O 7 is reported to undergo long-range magnetic order at 0.77 K (Ref. 24) and so doping with as much as 15% Zr may have been expected to have some effect on T N1 . In contrast, the second magnetic transition at T N2 is quickly removed by the perturbation introduced by the doping with Zr.…”