Relaxation and magnetocaloric effect in the Mn molecular nanomagnet incorporated into mesoporous silica: a comparative study

This paper presents the synthesis and investigation of the magnetic properties of mesoporous silica SBA-15 functionalized with Mn 12 ([Mn 12 O 12 (CH 3 COO) 16 (H 2 O) 4 ]·2CH 3 COOH·4H 2 O) high-spin molecular clusters. The SBA-Mn 12 sample has been examined by means of X-ray diffraction, infrared spectroscopy, nitrogen sorption and TEM techniques. AC and DC magnetic measurements, including measurements of the magnetocaloric effect (MCE) were carried out both for SBA-Mn 12 and for polycrystalline Mn 12 . An increase in the activation energy and in the distribution of relaxation times was observed for SBA-Mn 12 as compared to those of Mn 12 . Differences in the MCE were also revealed. The maximum magnetic entropy change at the field change of 50 kOe for SBA-Mn 12 is equal to 13.8 J K −1 mol −1 at T = 2.8 K, which is significantly less than 25.3 J K −1 mol −1 observed for Mn 12 at 3.2 K. The altered relaxation and the magnetocaloric effect point to a successful incorporation of Mn 12 molecules into the silica channels. Successful incorporation of the Mn 12 molecules into silica channels has been attested with AC susceptometry and magnetocaloric effect measurements.