Thermal switching provides an effective way for active heat flow control, which has recently attracted increasing attention in terms of nanoscale thermal management technologies. In magnetic and spintronic materials, the thermal conductivity depends on the magnetization configuration: this is the magneto-thermal resistance effect. Here we show that an epitaxial Cu/Co50Fe50 multilayer film exhibits giant magnetic-fieldinduced modulation of the cross-plane thermal conductivity. The magneto-thermal resistance ratio for the Cu/Co50Fe50 multilayer reaches 150% at room temperature, which is much larger than the previous record high. Although the ratio decreases with increasing the temperature, the giant magneto-thermal resistance effect of ~100% still appears up to 400 K. The magnetic field dependence of the thermal conductivity of the Cu/Co50Fe50 multilayer was observed to be about twice greater than that of the cross-plane electrical conductivity. The observation of the giant magneto-thermal resistance effect clarifies a potential of spintronic multilayers as thermal switching devices.Thermal switching enables active control of heat transfer, which is a key component of nanoscale thermal management technologies for electronic devices. 1,2 Towards the development of such technologies, thermal switching devices showing large thermal conductivity change, wide temperature range operation above room temperature, high heat exchange, and easy integration into existing electronic devices are desired.In this perspective, various solid-state thermal switching techniques, including metal-insulator transition, 3,4 electrochemical intercalation, 5,6 and electric field control of domain structures 7 and magnons, 8 have been investigated so far. However, development of thermal switching devices exhibiting large thermal conductivity change and wide temperature range operation remains major challenges.In the emerging field of spin caloritronics, the spin degree of freedom is introduced into thermal and thermoelectric transport phenomena to create novel physics and functionalities. 9,10 In particular, the thermo-spin and magneto-thermoelectric effects in magnetic materials and multilayer structures have been actively investigated since these phenomena offer an unconventional approach to develop energy harvesting and thermoelectric cooling devices with a simple structure, versatile scaling capability, and unique symmetry. 11-15 However, there are only several reports focusing on the active control of thermal conductivity based on spin caloritronics. [16][17][18] In magnetic and spintronic materials, the thermal conductivity depends on the magnetization configuration, which is called the magneto-thermal resistance (MTR) effect. 19 The MTR effect makes it possible to achieve not only large magnetic-field-induced change of thermal conductivity but also thermal switching with no-wiring, non-volatile, and wide temperature range operation. Because of these potential advantages, studies on the active control of thermal conductivity in ma...
