TM59 is a mid-high-frequency low-loss MnZn power ferrite with an initial permeability (μi) of 1900, a saturation flux density (Bs) of 530 mT at 25 °C (430 mT at 100 °C) and a Curie temperature above 260 °C. Its principal characteristic is high-frequency loss at large flux swing: 600 → 550 kW/m³ at 500 kHz / 100 mT, the lowest value in the power series at this high-flux operating point; 330 → 250 kW/m³ at 800 kHz / 60 mT and 80 → 50 kW/m³ at 500 kHz / 50 mT, with the 100 °C loss below the 25 °C loss at every operating point, i.e. a negative temperature coefficient of loss. The lowest remanence in the series (Br 35 mT at 100 °C) and a coercivity of 10 A/m keep hysteresis loss low, and 430 mT of hot-state Bs preserves the saturation margin of high-power transformers at 100 mT-class flux swings. Typical applications are 500–800 kHz high-power transformers, including LLC/CLLC main transformers in server and telecom supplies and high-power HF DC-DC converters; its 100 °C DC-bias capability is the highest of the eight grades measured (220 nH band, I@90 % = 48.4 A), so resonant and output inductors may use the same grade as the main transformer. Of the two mid-high-frequency grades TM59 is the recommended grade for new designs, TM50A the earlier generation (μi 2500, retained for existing designs); for inductor applications such as TLVR above 0.7 MHz the high-frequency grade TM65 is recommended.