A domain size effect in the magnetic hysteresis of NiZn-ferrites

Abstract

Hard magnetic properties of Mn-Ga melt-spun ribbons J. Appl. Phys. 112, 083901 (2012) Influence of chemical pressure in Sn-substituted Ni2MnGa Heusler alloy: Experimental and theoretical studies J. Appl. Phys. 112, 073921 (2012) Hysteresis effects in the inverse magnetocaloric effect in martensitic Ni-Mn-In and Ni-Mn-Sn J. Appl. Phys. 112, 073914 (2012) Magnetic and electronic properties of Fe and Ni codoped SnO2

Domain structure in polycrystalline MnZn ferrite imaged by magnetic force microscopy

“…9 are of the order of 1 to 1. we find ␦ m Ϸ1.3 m. In an independent experiment with a different and more sensitive setup ͑using a tip made magnetically sensitive by electron beam deposition͒, 17,18 we found for a NiZn ferrite a much smaller value of ␦ m ͑of the order of 0.2 m͒, reasonably consistent with a ten times smaller A and a ten times larger K for this ferrite. 5 In view of the value of ␦ m for the MnZn ferrite, it is also significant that the onset of the magnetic signal near the grain boundary in smallgrained samples ͑see Figs. 4 and 5͒ is found well within the grain, at a distance of more than 0.5 m from the boundary.…”

“…4,10 Even when taking into account that the grain is embedded in a soft magnetic environment, the upper limit for the estimates of D cr barely reaches the experimental value. 5,12 Moreover, the change in energy dissipation as function of grain size can be surprisingly sharp, taking place in less than 0.1 m. 5 Given the distribution of grain sizes inherent to ceramic materials, the expectation would be a more gradual change in the region where grains with single domains and two domains should coexist. Better understanding is clearly needed of the behavior of the magnetization and the domain wall in a grain in connection with its local environment.…”

“…3,4 For the MnZn ferrites to be discussed here, D cr is about 4 m. Recently, it was found from magnetic susceptibility measurements that the energy dissipation at MHz frequencies is substantially lower in samples with grain size DϽD cr , which was attributed to the absence of domain walls in these small grains. 5,8 Still, a number of questions persists. For instance, theoretical estimates for D cr of an isolated grain [9][10][11][12] yield values which are orders of magnitude lower than experimentally found.…”

“…1,2 Since this property is related to domain wall motion, several studies have been performed lately on the domain structure of poly-crystalline MnZn and NiZn ferrites, and its relation to the average grain size. [3][4][5] The latter parameter can be controlled by the sinter temperature in the preparation process and allows tuning of the grain size with small size distributions from below 1 m to above 10 m while maintaining a constant composition. 6,7 Due to the low magneto-crystalline anisotropy of certain MnZnferrite compositions, the domain wall size can be very large, of the order of 1 m, so that the grain size can be varied from below to above the domain wall size.…”

Low-Temperature Synthesis of Nanocrystalline Mn<sub>0.2</sub>Ni<sub>0.8</sub>Fe2O<sub>4</sub> by Oxalate Precursor Route

“…Spinel nanocrystalline ferrite displays enhanced magnetic and electronic properties by virtue of their unique electronic or physical structure which may be harnessed for technological applications [2,4,19,20]. Moreover, some phenomena like modified saturation magnetization, superparamagnetism, metastable cation distributions, etc., have been observed in nanoparticles of various ferrites [18,21,22].…”