ESR measurements at ultra-low temperatures using a dilution refrigerator

Takuo Sakon, Hiroyuki Nojiri, Keiichi Koyama, Takayuki Asano, Yoshitami Ajiro, Mitsuhiro Motokawa

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


An ESR measurement system with a high sensitivity vector network analyzer has been developed for use at ultralow temperatures below 1 K. The microwave frequency can be varied between 45 GHz and 110 GHz. The resonant cavity was installed in a bottom of a 3He-4He dilution refrigerator, which realizes the temperatures down to 160 mK. In order to avoid a heating of the cavity and sample by microwaves or heat leaks, attenuators and thermal anchors were placed at suitable positions. As the first experiment, the ESR was measured on a quantum spin chain Cu benzoate down to 160 mK, in which a field-induced gap was recently found. The evaluation of a new ESR mode, so called breather mode, was found at the lowest temperatures. In the previous ESR down to 0.5 K, this mode was clearly found for H∏ c, in which the magnitude of the gap is largest. In the present work, the achievement of low temperatures enabled us to observe a smaller gap in H∏ b by suppressing of the thermal excitation.

Original languageEnglish
Pages (from-to)140-144
Number of pages5
Journaljournal of the physical society of japan
Issue numberSUPPL. B
Publication statusPublished - 2003
Externally publishedYes


  • Cu benzoate
  • Dilution refrigerator
  • Electron spin resonance
  • Quantum spin system
  • Vector network analyzer

ASJC Scopus subject areas

  • Physics and Astronomy(all)


Dive into the research topics of 'ESR measurements at ultra-low temperatures using a dilution refrigerator'. Together they form a unique fingerprint.

Cite this