We investigate the piezomagnetic effect in pyrochlore-type oxides ${\mathrm{Y}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and ${\mathrm{Cd}}_2{\mathrm{Os}}_2{\mathrm{O}}_7$, which exhibit a noncoplanar magnetic structure called the all-in/all-out antiferromagnetic order at low temperatures. The all-in/all-out magnetic order can be viewed as a ferroic order of the $xyz$-type magnetic octupoles. In both oxide materials, we observe a linear increase in magnetization with applied stress. We then estimate the powder-averaged piezomagnetic tensor at the lowest measured temperature 10 K to be $Q=6.36\times {10}^{-6}$ ${\mu }_{\text{B}}/\mathrm{Ir}/\mathrm{MPa}$ for ${\mathrm{Y}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and $Q=3.83\times {10}^{-7}$ ${\mu }_{\text{B}}/\mathrm{Os}/\mathrm{MPa}$ for ${\mathrm{Cd}}_2{\mathrm{Os}}_2{\mathrm{O}}_7$. We discuss the microscopic mechanism of the piezomagnetic effect based on the stress-induced modification of the g-tensor anisotropy and Dzyaloshinskii-Moriya interactions. This work supports further development of piezomagnetic materials using magnetic multipoles.

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• Antiferromagnetism
• Spin-orbit coupling
• Multiferroics
• Transition metal oxides
• Magnetization measurements
• Pressure effects