50 MeV, Li~(3+) - Ion Irradiation Effect On Magnetic Ordering Of Y~(3+) - Substituted Yttrium Iron Garnet

摘要

This communication presents the effect of non-magnetic Y~(3+) ions substitution for magnetic Fe~(3+) ions and 50 MeV, Li~(3+) ion irradiation (fluence: 5 x 10~(13) ions/cm~2) on magnetic ordering and Neel temperature of Y_(3+x)Fe_(5-x)O_(12) (x= 0.0, 0.2, 0.4 and 0.6) garnet system, studied by means of X-ray powder diffractometry and thermal variation of low field (0.5 Oe) ac susceptibility measurements. The un-irradiated compositions exhibit normal ferrimagnetic behavior with decrease in transition temperature (T_N) on increasingY~(3+)- concentration (x). The irradiated counterparts are characterized by tailing effect indicative of non-uniform effect of irradiation and lower value of T_N. The results have been discussed based on the weakening of magnetic exchange interactions and cumulative effect of redistribution of cations and fractional creation of localized paramagnetic centers resulting from swift heavy ion irradiation. The Neel temperatures and exchange integrals have been calculated theoretically.