This story is a bit confused.
Data in chips is recorded and stored as the spin of electrons
Not usually it isn't, that's actually the bigger news all by itself.
From the headline I was expecting a story about 3-d layered conventional chips, but then out of the blue you just casually drop in that it's spintronics as well? Did you not realise that the spintronics aspect of this is by far the more new and innovative cutting-edge technology? Conventional chips are being developed in 3-d, but that's just routine engineering r'n'd; spintronics is the real innovation here.
Also, the existing chips you're talking about are MRAM, not MDRAM, and they aren't really very spintronic. Magnetism is based on electron spin, and they store bits in magnetically charged cells, but hell, so did cassette tapes and they're not spintronic; it becomes spintronics when you're actually moving electron spins around the place as your primary 0/1 signalling mechanism. So, yes, there are magnetic cells in which the spin of bound electrons is polarised one way or the other, but they're immediately read out into simple spin-irrelevant conventional circuits to go from the cells round the rest of the chip. You write as if spintronics was an established technology and 3-d chips were something radically new, when it's actually the combination of the two that is the story here.