  Gd2GaSbO7 and Gd2InSbO7 pyrochlore compounds exhibit quantum fluctuations in
a spin ice-like state. These compounds have not been adequately studied based
on the concept of magnetic frustration. Here, we have synthesised and
characterised Gd2GaSbO7 and Gd2InSbO7 to investigate their ground-state
magnetic properties. We confirmed the cubic pyrochlore structure via X-ray
powder diffraction. Magnetic and heat capacity measurements show an absence of
magnetic order down to 400 mK. Interestingly, the low-temperature magnetic heat
capacity of Gd2GaSbO7 and Gd2InSbO7 exhibits a broad maximum around
T_{\text{max}} = 0.9 K and T_{\text{max}} = 1 K, respectively. The
low-temperature Cmag data fit with the power-law C_{\text{mag}} \approx
T^{\frac{d}{n}} with dependencies of T^{1.71} for Gd2GaSbO7 and T^{1.49} for
Gd2InSbO7, suggesting spin fluctuations caused by the disorder of magnetic
moments at low temperatures. Both compounds retain residual entropy akin to
water ice, resembling the spin ice state. Additionally, we analysed the ratio
between nearest-neighbour exchange and dipolar interaction for all reported
Gd-based pyrochlores, finding that Gd2InSbO7 has the lowest and weakest
exchange interaction among them. This indicates that chemical pressure affects
exchange interaction due to the different pathways of mediators between
magnetic ions. This study reveals robust quantum fluctuations in the ground
state in GGSO and GISO, similar to quantum spin ice compounds such as Pr2Zr2O7,
Pr2Sn2O7, and Yb2GaSbO7. Other Gd-pyrochlore compounds exhibit long-range
magnetic order, which is in stark contrast to this.
