24.06.2011
РОССИЙСКАЯ АКАДЕМИЯ НАУК

УРАЛЬСКОЕ ОТДЕЛЕНИЕ

ИНСТИТУТ ХИМИИ TBEPДОГО ТЕЛА
   
| | | | |
| | | | | |
 24.06.2011   Карта сайта     Language По-русски По-английски
Новые материалы
Экология
Электротехника и обработка материалов
Медицина
Статистика публикаций


24.06.2011

Light-induced spin-crossover magnet





Journal name:

Nature Chemistry

Volume:

3,

Pages:

564–569

Year published:

(2011)

DOI:

doi:10.1038/nchem.1067


Received


Accepted


Published online




The light-induced phase transition between the low-spin (LS) and high-spin (HS) states of some transition-metal ions has been extensively studied in the fields of chemistry and materials science. In a crystalline extended system, magnetically ordering the HS sites of such transition-metal ions by irradiation should lead to spontaneous magnetization. Previous examples of light-induced ordering have typically occurred by means of an intermetallic charge transfer mechanism, inducing a change of valence of the metal centres. Here, we describe the long-range magnetic ordering of the extended FeII(HS) sites in a metal–organic framework caused instead by a light-induced excited spin-state trapping effect. The FeNb-based material behaves as a spin-crossover magnet, in which a strong superexchange interaction (magnetic coupling through non-magnetic elements) between photo-produced FeII(HS) and neighbouring NbIV atoms operates through CN bridges. The magnetic phase transition is observed at 20 K with a coercive field of 240 Oe.




left


  1. Figure 1: Crystal structure of Fe2[Nb(CN)8]·(4-pyridinealdoxime)8·2H2O.


    a, Coordination environments around Fe and Nb. The Fe atom is coordinated by two cyanide nitrogen atoms of [NbIV(CN)8] and four pyridyl nitrogen atoms of 4-pyridinealdoxime. Four CN groups of [NbIV(CN)8] are bridged to four Fe centres, and the other four remain free. Red and green ball-sticks represent the [FeN6] and [NbC8] moieties, respectively. Light blue, blue and pink balls represent C, N and O atoms in 4-pyridinealdoxime. b, Cyano-bridged FeNb three-dimensional framework viewed along the c-axis. c, View from the diagonal direction. 4-Pyridinealdoxime molecules are drawn as light blue wire frames or orange sticks with planes. Zeolitic water molecules are omitted for clarity. d, Organic ligand molecules of 4-pyridinealdoxime are drawn as spheres, considering their van der Waals radii. Light grey, grey, blue and red spheres denote C, H, N and O atoms, respectively. Small red and green balls and grey sticks represent Fe and Nb atoms and the cyano-bridged FeNb framework, respectively.




  2. Figure 2: Spin-crossover transition phenomenon.


    a, Temperature T dependence of the molar magnetic susceptibility χM measured in an external field of 5,000 Oe. The decrease in the χMT value with decreasing temperature indicates the transition from the high-T form to the low-T form, which is due to the spin-crossover from FeII(HS)(S = 2) to FeII(LS)(S = 0). Squares and circles denote χMT values with decreasing (blue arrow) and increasing (black arrow) temperature, respectively. Inset: schematic illustration of the electronic configuration of FeII(HS) and FeII(LS). b, Temperature dependencies of the differential UV–vis absorption spectra from 300 K to 100 K in 20 K intervals. As the temperature decreases, the variable-temperature UV–vis absorption spectra exhibit optical absorptions around 480 nm (band I) and 650 nm (band II). Inset: schematic illustration for the ground and excited states of FeII. Arrows indicate the dd transitions of band I (1A11T2) and band II (1A11T1) on FeII(LS). Measurement errors are included within the marks and lines.




  3. Figure 3: Photo-induced magnetization caused by light-induced spin-crossover.


    a, Magnetization versus temperature curves at 100 Oe. Light irradiation induces a spontaneous magnetization with a Curie temperature of 20 K. b, Magnetic hysteresis curves at 2 K. After irradiation, a magnetic hysteresis loop with a coercive field of 240 Oe appeared. Blue and red circles denote measurements before and after irradiation with 473 nm light. Measurement error is included within the marks.




  4. Figure 4: Mechanism of light-induced spin-crossover ferromagnetism.







Дизайн и программирование N-Studio 
А Б В Г Д Е Ё Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ъ Ы Ь Э Ю Я
  • Chen Wev   honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

  • © 2004-2024 ИХТТ УрО РАН
    беременность, мода, красота, здоровье, диеты, женский журнал, здоровье детей, здоровье ребенка, красота и здоровье, жизнь и здоровье, секреты красоты, воспитание ребенка рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок медицина, клиники и больницы, болезни, врач, лечение, доктор, наркология, спид, вич, алкоголизм православные знакомства, православный сайт творчeства, православные рассказы, плохие мысли, православные психологи рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок